Along these lines, if we pretend there is actually a zero percent chance of curing death in our lifetime, how should we rationally act differently? Often people use the cliche 'if you were going to die tomorrow what would you do differently today?' as a thought experiment, seemingly implying (to me at least) that we're already living rationally for an ~80 year lifetime and that only changes in behavior should come from learning you have a very short time to live left.

I often wonder if I too easily approximate ~80 years as infinity in my reasoning about life, and that I'm not appropriately taking into account an 80 year life span (or much shorter if you subtract sleep, how old you are now, and years of life you think you'll be healthy enough to have control over).

TLDR: I think it's hard to reason about spans of time that are longer than we've experienced but shorter than infinity, and I don't know what to do about it.