This is silly. On a pragmatic and humanistic level, the reward is offered in the future and no single action or lack of action today eliminates the possibility of receiving the reward. If your argument were true no one would smoke since the analogous argument is "I offer you extra years of healthy life (off in the future) if you stop smoking." The smoker thinks "well, maybe so but I can get away with this cigarette and the next one."

As to the theological argument, I certainly agree that those who believe in young Earth Creationism, the "Answers in Genesis" crowd, and those who say "if your science and evidence disagree with the Bible, your science and evidence are wrong" are likely to be hypocritical in this sense. But those who say "the Bible is a guide inspired by God for the people of its time, that mistranslations, spurious additions and deletions, etc. have removed some of its original meaning, and the allegories are to make points, just as are Jesus' parables, and I have faith that God exists, Jesus died for my sins, and I can be forgiven" are the vast majority of Christians. Your argument says nothing to them.