I think a lot of my positions on immortality and perfection as undesirable and otherwise useless things are derived from a composite of various positions set forth in fiction, so I'll post those ideas as I found on wikipedia. I'm not familiar with all of them and some are more satirical than serious, but I think the point is made much better with each example.
Since immortality is seen as a desire of humanity, themes involving immortality often explore the disadvantages as well as the advantages of such a trait. Sometimes immortality is used as a punishment, or a curse that might be intended to teach a lesson. It is not uncommon to find immortal characters yearning for death. A similar, though somewhat different theme, concerned Elves and Men in Middle-earth. While the immortality of Elves was not explicitly a curse, the mortality of Men was viewed as a gift, albeit one that was not understood by those possessing it. This was chiefly due to the Elves' clear faculty of memory, which could accumulate millennia of sad experiences.
In some parts of popular culture, immortality is not all that it is made out to be, possibly causing insanity and/or significant emotional pain. Much of the time, these things only happen to mortals who gain immortality. Beings born with immortality (such as deities, demigods and races with "limited immortality") are usually quite adjusted to their long lives, though some may feel sorrow at the passing of mortal friends, but they still continue on. Some Immortals (such as certain deities, demigods, and intelligent undead) may also watch over mortal relations (either related to or descended from them), occasionally offering help when needed.
In his short story 'The Immortal', Jorge Luis Borges treats the theme of immortality from an interesting perspective: after centuries and centuries, everything is repetition for the immortal and a feeling of ennui prevails. The immortal, who had turned so after drinking from a certain river, is set to wander the world in search for that same river, so that he can become mortal again.
In the manga Blade of the Immortal, Manji is a samurai who has been cursed with immortality. Only after slaying 1000 evil men will the curse be broken so he can finally die. His body cannot age nor can he die from physical wounds. Manji's sword skills are sloppy due to the fact that since he's immortal he doesn't need to know how to fight properly.
There is another immortal character in the Naruto series named Hidan, who claims to be the slowest attacking member in his group and is considered stupid by his partner, because he attacks without thought for the consequences. It is possible he did not gain these skills because he did not believe he would need them, being an immortal. This could hardly be further from the truth: Hidan is now a disembodied head buried under a ton of rock, and yet cannot die.
In Jonathan Swift's Gulliver's Travels, some of the inhabitants of the island of Immortals (near Japan) don't die, but they age and became ill, demented and a nuisance to themselves and those surrounding them. Swift presents immortality as a curse rather than a blessing.
The film Zardoz also depicts a dystopian view of immortality, where interest in life has been lost and suicide is impossible.
The Star Trek: Voyager episode "Death Wish" explored in depth the existence of the omnipotent, immortal and omniscient aliens Q. It is learned in that episode that the aliens were originally human-like, and somehow evolved into their current state long ago. With their new-found powers, the Q set out to fully explore, experience and understand the universe. Afterwards, the Q had nothing left to do or say, and now they simply sit out eternity in their realm. As one Q explained, you can only experience the universe so many times before it gets boring, with this Q- a former philosopher- now seeking to commit suicide as it is the only thing he hasn't done.
In the children's novel, Tuck Everlasting by Natalie Babbitt, a family is made physically immortal by drinking water from a magical spring. They are trapped at the same age forever and are invulnerable. They are hated by the ordinary people who knew them and are forced to watch as everything they cherish grows old and dies.
In the film and television series Highlander, once one dies for the first time, if they are an Immortal, they will spend the rest of eternity at that physical age. This poses a problem when one dies as a small child, or as a very old man. The same is true of the Claudia character in Anne Rice's Interview with the Vampire, who became a vampire while still only a child, and the Blade television series.
In the Supernatural third season episode "Time is On My Side", Dean and Sam Winchester face Doctor Benton, a doctor who discovered the secret to eternal life in 1816. However, although his process keeps him alive, he must constantly replace his damaged and worn-out body parts to operate relatively comfortably; taking out his heart will only inconvenience him for a time, but his entire body has noticeable stitches all over from where he has taken organs from other people to add them to his own body. At the conclusion of the episode, the Winchesters bury him in a grave after tying him up so that he will be forced to endure an eternity buried alive.
In the film Hocus Pocus, while three witches seek immortality by sucking the life essence of children, they also curse one of their enemies, a young man named Thackery Binx, to become an immortal black cat to punish him for trying to stop them draining his sister's life-force so that he will be condemned to live forever with the guilt of not saving her. As a result, Binx remains alive as a cat for over three hundred years, capable of surviving even such accidents as getting run over by a bus- the bus killing him only for him to revive a few moments later-, until the witches who cursed him are brought back to life by a curse they cast shortly before their executions, their subsequent deaths when the sun rises ensuring that their curse is lifted.
In general, a theme seen with many variations, is the notion of an essential world weariness akin to extreme exhaustion for which death is the only relief. This is inescapable when immortality is defined as (half) infinite life. Immortality defined as finite but arbitrarily long per the desire to exist does not, as a definition, suffer this limitation. When a person is tired of life, even death is shut off to them, creating an endless torture, as evidenced in the Bill Murray movie Groundhog Day, where a character is trapped in an endlessly repeating time loop that causes him to live the same day over and over again even when he tries to kill himself before the end of the cycle.
Immortality can be achieved in fiction through scientifically plausible means. Extraterrestrial life might be immortal or it might be able to give immortality to humans. Immortality is also achieved in many examples by replacing the mortal human body by machines.
In Doctor Who mythology, the Cybermen are basically human brains placed into mechanical bodies, with every emotion drained out. This process was supposed to allow the Human race to reach its pinnacle. The unforeseen downturn is that with immortality reached, there is no motivator for the Human Race to actually strive for anything more.
Another example of immortality in Doctor Who is found in the character Jack Harkness, a companion to the Ninth and Tenth Doctors, who was unintentionally transformed into a 'fact' of the timeline when fellow companion Rose Tyler temporarily acquired omnipotent power and brought him back to life after he was killed by the Daleks; unused to the power, Rose didn't just bring him back to life, she 'brought [him] back forever'. Although he ages at a very slight rate - having grown only the occasional grey hair despite having been alive for over two millennia since he was resurrected - Harkness is capable of recovering from any potentially fatal injuries within moments, although some forms of death take him longer to recover from than others; a bullet to the head only put him down for a few seconds, but he required at least a few minutes to come back after being thrown from the roof of a tall building, while it took him the better part of a day to recuperate after he was killed via a bomb in his stomach (Although the fact that he was able to regenerate his entire body when reduced to only an arm, a shoulder and part of his head should not be overlooked).
In the Doctor Who spin-off series Torchwood, Jack's colleague Owen Harper acquired a similar kind of immortality when he was brought back to life after being shot. Owen becomes technically dead, and thus incapable of eating, drinking, sleeping, having sex, and healing injuries. However, for all practical purposes, he cannot be killed, apparently lacking the need to breathe and displaying a general immunity to pain, as demonstrated by his not noticing when he cuts his left hand. Owen compares his new state to Jack by saying that, while Jack will 'live forever', he is destined to 'die forever'.
Torchwood's fourth series, Torchwood: Miracle Day, explored what would happen if the whole world became immortal, when an attempt by a mysterious group of three families to gain power resulted in all human life on Earth losing the ability to die (Although the formerly-immortal Jack Harkness became mortal at the same time). However, while they cannot die, they can still get sick and injured and their ability to heal has not been affected, with the result that a suicide bomber's body is left totally pulverized even while he appears to retain some form of consciousness, team member Rex Matheson has to deal with constant pain from the wound in his chest where he was impaled by a rebar in a driving accident, and a woman retains consciousness even after her car is crushed in a car compacter with her still inside it. This is eventually undone and Jack's immortality restored, with all patients classified as 'Category One' under the new medical rules- being fatally injured to the point where the Miracle was the only reason they hadn't died yet- being given a brief moment of clarity and peace before they died.
Megaman Zero's Doctor Weil had his memories transferred into program data and his body remodeled into that of a cyborg's as punishment for sparking the Elf Wars, using the Dark Elf to attack Reploids and humanity alike. He was then banished from nature and humanity, which eventually drove him insane.
Both series feature "ascended beings," such as the Ancients, who have learned to shed their physical body and exist as energy, making them immortal. Another species in the series, the Asgard, have mastered a form of immortality, by transferring their minds into cloned bodies when their original form sustains serious injury, but by the time they encounter Earth they have begun to die due to their genetic structure breaking down as a result of being cloned so often, the race committing mass suicide at the conclusion of SG-1 to spare themselves the pain of the death that now awaits them after recognising that they cannot save themselves.
Perry Rhodan is the world's most prolific literary science fiction (SF) series, published since 1961 in Germany. In the storyline Perry Rhodan is the commander of the first mission to the moon, where they come upon a stranded vessel of an alien race in search of eternal youth. Perry Rhodan uses the superior technology to unite the earth and then continues the search for eternal youth. Ultimately he follows the hints laid out by a higher being called ES ("it" in German) that exists in an incorporeal state. This being chooses Perry Rhodan and a select few of his companions to attain Agelessness in order for them to pursue goals set by ES. ES says "I grant you everlasting life, not rejuvenation." Over the course of the series, there is a side-plot, which focuses on the downsides of immortality: It is hard to engage in relationships, when your partner ages and dies off. Similar problems occur with children.
In the Hyperion Cantos Universe, the TechnoCore, a group of sentient artificial intelligences which parasitized humanity, created a parasite called the cruciform. It was first tested in the planet Hyperion, and it is able to regenerate a human body along with personality and memories after death. The cruciforms are a flawed success as there is a loss of intelligence and genetic decay after each resurrection, rendering asexuated humans with little intelligence. However, when the TechnoCore offers it to the Catholic Church in a secret alliance to be able to keep with the need of parasitism over humanity, any error in personality and memories in the resurrection creche fixed through a process that only some priests in the Catholic Church know. This effectively brings perfect immortality to any human who abides to follow the laws of the Catholic Church. Even in the case of a disastrous death, the smallest cruciform remnant is enough to recreate the whole human body again, given the right conditions. However, the main characters in the story debate about the ethics and benefits of immortality, reaching to the conclusion that it stalls the evolution of humankind and it's severely counterproductive to any long-term expectations.
In the LucasArts adventure game The Dig, the remains of an alien civilisation advanced enough to gain first physical and then spiritual immortality are explored and analysed. It eventually turns out that the obsession with living forever ultimately brought about their downfall; they lived forever, but lost "everything that made life worth living".
Most of the novels by Alastair Reynolds feature immortal characters of some form or another, usually made possible by advanced medical technology and periodic regeneration of one's body. One of the issues discussed in these novels, particular Chasm City, is the manner in which characters deal with their immortality and the boredom it inevitably generates. The Conjoiners, the most advanced faction, are able to modify their brains to the extent that they simply do not experience boredom at all. Unaugmented humans typically suffer intense boredom and attempt to reduce this by taking part in increasingly dangerous and exciting activities.
In the Instrumentality of Mankind universe by Cordwainer Smith, there's a drug which allows to delay aging indefinitely in humans, called stroon or Santaclara drug. However, the Instrumentality is very aware of the dangers of immortality, so every human being can only take stroon up to a life of 400 years. Although there are exceptions, for example if a person is thought to be valuable for humankind, no one is allowed to live longer than 1,000 years. Thus, although humankind could achieve immortality, they avoid it consciously.
