That's the same way I see it. I regularly climb with guys in their late 50's who are still beasts, and when doing a few cross country races a few years back you see guys of all ages.
Adele seems to think that fitness also has a time limit, and that if she has kids later, she'll be too tired to keep up with them. I disagree and don't have an issue with the prospect of having kids while I'm older. Just don't want them now, or any time in my 20's....