How would the recognition of extreme longevity or even living forever change the way we would behave (or should behave)?

I think as we go there's an imbalance of focus on living for today that is often so ingrained it would be beyond comprehension for most people to even really think on for very long in a serious way. I would say, knowing humanity, if people thought about it too much, they would probab5 be so focused on future, they would either not live today to the fullest, or the evil ones would how much bad they could get away with, if there was no future penalty.