Why is it almost impossible to break through to people in their 80s or 90s who are still rebelling against God?

Les explains that the same pattern seen in Pharaoh appears in human nature today. During the plagues, Moses repeatedly asked whether Pharaoh was ready to let the Jews go; Pharaoh could have said, "Let them go," but instead said, "I'll not let them go." He chose his own direction. Les applies this: when people are brought to decide for or against God and say no, the next time it is easier to say no. Their concept of rebellion grows, and their recognition of God's mercy gets smaller. That is why, when people get into their 80s and 90s and are still rebels against the grace of God, it is hard to break through—almost impossible—because they have become so hardened. Les notes he has talked to a few and you just cannot get through to them; sometimes you can, but usually it is so hard. Every time they were confronted with believing the gospel and rejected it, it became harder to break down those barriers of resistance. So it was with Pharaoh.