It's easy to talk about what you want to be doing in your fifties, but nobody wants to talk about what they'll be doing when they're 100.
It's easy to assume we'll make it to 50, but nobody really believes they'll make it to 100. Most don't make it to 100, but many don't make it to 50 and yet we all assume we'll be going strong at 50 years old.
So I'm going to start saying "WHEN I'm 100 years old, I want to be doing X, Y, or Z..." It's easy to do that for age 50, but I want to be more optimistic. So "100" it is, maybe "105" just to keep things interesting.