There is no evidence in any scripture or liturgy or anything of salvation after death, but for Christ's harrowing of Hell in which those who died before the coming of Christ were freed. The scriptures teach otherwise in several places:
Luke 16:19-31 (Lazarus and the rich man) has Abraham say in reply to the pleas of the rich man in Hades "Son, remember that in your lifetime you received your good things, and likewise Lazarus evil things; but now he is comforted and you are tormented. And besides all this, between us and you there is a great gulf fixed, so that those who want to pass from here to you cannot, nor can those from there pass to us." (NB: Not "Oh, okay, sure, come on out...")
We have also Christ's own words in Matthew 25:41 "Depart from me, you who are cursed, into the eternal fire prepared for the devil and his angels" (emphasis mine).
In Revelation 20:10 "And the Devil who deceived them was thrown into the Lake of Fire and Brimstone, where the beast and the false prophet are also; and they will be tormented day and night forever and ever." (emphasis again mine)
And in the liturgy of St. Basil (the core of which dates to the 4th century), the priest prays: "He rose from the dead on the third day; He ascended into the heavens, and sat at Your right hand, o Father; He has appointed a day for recompense, on which He will appear to judge the world in righteousness and give each one according to his deeds." (emphasis added) We respond to this by pleading that the judgment be "According to your mercy, O Lord, and not according to our sins."
What sense would any of this make if in fact we could simply choose after having died to accept that which we would not accept in life? In fact, the error of that kind of thinking is also exposed in the story of Lazarus and the rich man mentioned earlier, which continues:
“Then he said, ‘I beg you therefore, father, that you would send him to my father’s house, for I have five brothers, that he may testify to them, lest they also come to this place of torment.’ Abraham said to him, ‘They have Moses and the prophets; let them hear them.’ And he said, ‘No, father Abraham; but if one goes to them from the dead, they will repent.’ But he said to him, ‘If they do not hear Moses and the prophets, neither will they be persuaded though one rise from the dead.’"
The bottom line is that salvation is not the intellectual acceptance of some piece(s) of information -- as in the Mormon scheme which apparently leaves everything up to the will of those who have already died to affect their own salvation -- but the life, death, and resurrection of Jesus Christ our Lord, by which the power of sin and death is broken. That is what has freed our race from eternal torment in Hell, and we must not deign to live according to it in the hopes that somehow, despite all the evidence to the contrary, God means something other than "eternal" when He warns of the punishment of the wicked after death.
You can't do whatever you want in life and then just decide afterwards that you're done and now you'll take things seriously. Do you think God is stupid? Like He'll just say "Oh, okay...I mean, I wanted you to follow Me in life, but I guess you didn't want to, but now that you see the reward for that, you've decided to do what I asked of you. And here I thought I gave you life so that you could be serious with it. Silly me."?
Don't treat God like an idiot who doesn't know what He's doing. He does know, and those who follow Him know. Mormonism, notably, does not know, or else it wouldn't advance such a horribly anti-God doctrine.
There are people who lived a good life and repented of their sins but were not baptized and didn't have that opportunity when they were alive. Would a fair God banish them to Hell for eternity? What about Lazarus, was he baptized? What about the thief that was on the cross, was he baptized? Were the Samaritans baptized? There are many who will need this saving ordinance done for them. I agree with you that a person can't do whatever you want in life and then just decide afterwards that you're done and now you'll take things seriously.
(New Testament | Romans 9:13 - 33)
13 As it is written, Jacob have I loved, but Esau have I hated.
14 What shall we say then? Is there unrighteousness with God? God forbid.
15 For he saith to Moses, I will have mercy on whom I will have mercy, and I will have compassion on whom I will have compassion.
16 So then it is not of him that willeth, nor of him that runneth, but of God that sheweth mercy.
17 For the scripture saith unto Pharaoh, Even for this same purpose have I raised thee up, that I might shew my power in thee, and that my name might be declared throughout all the earth.
18 Therefore hath he mercy on whom he will have mercy, and whom he will he hardeneth.
19 Thou wilt say then unto me, Why doth he yet find fault? For who hath resisted his will?
20 Nay but, O man, who art thou that repliest against God? Shall the thing formed say to him that formed it, Why hast thou made me thus?
21 Hath not the potter power over the clay, of the same lump to make one vessel unto honour, and another unto dishonour?
22 What if God, willing to shew his wrath, and to make his power known, endured with much longsuffering the vessels of wrath fitted to destruction:
23 And that he might make known the riches of his glory on the vessels of mercy, which he had afore prepared unto glory,
24 Even us, whom he hath called, not of the Jews only, but also of the Gentiles?
25 As he saith also in Osee, I will call them my people, which were not my people; and her beloved, which was not beloved.
26 And it shall come to pass, that in the place where it was said unto them, Ye are not my people; there shall they be called the children of the living God.
27 Esaias also crieth concerning Israel, Though the number of the children of Israel be as the sand of the sea, a remnant shall be saved:
28 For he will finish the work, and cut it short in righteousness: because a short work will the Lord make upon the earth.
29 And as Esaias said before, Except the Lord of Sabaoth had left us a seed, we had been as Sodoma, and been made like unto Gomorrha.
30 What shall we say then? That the Gentiles, which followed not after righteousness, have attained to righteousness, even the righteousness which is of faith.
31 But Israel, which followed after the law of righteousness, hath not attained to the law of righteousness.
32 Wherefore? Because they sought it not by faith, but as it were by the works of the law. For they stumbled at that stumblingstone;
33 As it is written, Behold, I lay in Sion a stumblingstone and rock of offence: and whosoever believeth on him shall not be ashamed.
