I suppose that an absence from Christianity might make a person come back stronger (as seems to have happened to robhu) or more mature, or something. Nevertheless, I bet there are de-converts who stay that way until they die. Given the traditional Christian view that you only get a chance to become a Christian in this life (e.g. Hebrews 9:27) and that people who reject God in this life go to Hell, it's hard to see how that would result in the person getting to know God better.

If God's desire is that people come to know him, the cut-off at death has always seemed arbitrary to me: it's almost as if someone was attempting to work out an explanation for what we observe to happen (people live and then die), rather than designing what happens for a particular purpose.