When is it too late to ask for salvation?
It is never too late, as long as a person is alive. The thief on the cross is a good example of this in the Bible.
What about obtaining salvation after death?
Some Christians believe that everyone will be given a second chance to believe after death. Usually the proof text used is:
1 Peter 3:18-20 (NIV)
18 For Christ also suffered once for sins, the righteous for the unrighteous, to bring you to God. He was put to death in the body but made alive in the Spirit. 19 After being made alive, he went and made proclamation to the imprisoned spirits — 20 to those who were disobedient long ago when God waited patiently in the days of Noah while the ark was being built. In it only a few people, eight in all, were saved through water,
To extract from this passage a doctrine that everyone will have a chance to be saved after death is quite a drastic stretch - especially since it is found nowhere else in Scripture. While I'm not sure about the meaning of this passage, it simply does not support that:
- Anyone besides the people described heard or will hear Jesus's proclamation.
- Anyone that heard Jesus's proclamation was given a chance for salvation.
These claims, which are necessary for the doctrine of obtaining salvation after death, are not supported by this passage.
Is it better to wait as long as possible to be saved?
No. It sounds like you may have the notion that when you are saved, you are saved from your past sin, but not your future sin. If this were true, then no one would be saved - no matter how "good" someone becomes after they become saved, no one is able to meet God's perfect standards.
When we are saved, God will conform us to the likeness of Christ through sanctification, but understand that no one undergoes this process perfectly. On the day of redemption, we will be justified - not because of our works, or our ability to keep from "screwing up", but because of our inclusion in Christ, and his sacrifice for us.