For example, a Christian might give away all their possessions, rejoice at the death of their children in circumstances where they seem likely to have gone to heaven, and generally treat their chances of Heaven vs Hell as their top priority.

Steven Landsburg used this reasoning, combined with the fact that Christians don't generally do this, to conclude not that Christians don't act on their beliefs, but that Christians don't generally believe what they claim to believe. I think the different conclusion is reached because he assigns a lot more rationality to people than you do. But certainly there are, for some people, very strong incentives against admitting that you've stopped believing in God.