I just bought my "Geezer Pass". Not that I consider 62 old, either. I've waited a long time for the damn thing, so I'm rather proud of it. Might just buy a second at that price so I can just leave one in each glove compartment. No more shelling out $80 per year.
My current "hiker hero" is a 75 year-old friend who I have a hard time keeping up with. After about 3K' of vertical I can usually catch up to him, but before that - he's way ahead.
Attitude plays a large role, but you can't ignore genetics, either. They're both factors.