Couldn't we argue that humans are not discrete. We are always changing, and we are connected to everything else in the world. If God is going to save anybody then he must save everybody and everything - past, present, and future. In a sense, we die every moment and we are born every moment, and we exist only in our imagination.
Another way of looking at this is that we all live eternally, because we exist in God's eternal mind. Personally, I want death to be the end of me.
Biologically it's true that our cells are always dying and being replaced with new ones. It's also true that our minds are quite mutable and so our personal identity, as far as the neurology of our brains and our ever-shifting and changing psychology goes, is shifting, changing, etc. In a large way who we are today can be quite different from who we were yesterday and who we will be tomorrow.
Though at the same time there is something of an identity, barring major brain injury or trauma, our experiences over a lifetime have shaped us. And while memories are somewhat subjective, the impression on us from an experience is still there, informing our self. Further, at the biological level we are a rather specific set of genetic instructions, we are encoded in our DNA. But more importantly--as far as Christianity is concerned--there is something of a permanence to our personhood and identity, that rather nebulous and hard-to-define something that we often call "the soul". There is a
something about us which makes us more than just bio-chemical clockwork. The human creature, in Christian teaching, is a psychosomatic creature, we are both body and soul, and both are fundamentally what makes me
me. The fallenness of the soul and the mortality of the body are, in Christ, redeemed and set forward in and by Him to an eternal permanence in the resurrection and Age to Come.
Crucially, our salvation is the salvation from the impermanence of our own present mortality. Resurrection means more than just the mere resuscitation of the body, it is the full renewal, restoration, and reconstitution of what and who we are, specifically, who and what we are in Christ. The drunkard is not raised again as a drunkard, the liar is not raised again as a liar, the paraplegic is not raised again as a paraplegic, the leper is not raised again as a leper. All that was injured, broken, and fallen shall be healed and restored, and all that is good shall be ever the more good. Nothing good shall be lost.
How all this actually looks and plays out is unknown, we but see through the glass dimly.
-CryptoLutheran