When I was 30 and dancing #TangoArgentino in the #ConfiteríaIdeal (one of the oldest #Milonga venues) in Bs Aires I was asked to dance by an older tanguero: noticeable flexibility, energy + physical agility in person.
Thought he must have been about 60.
Nope.
The gentleman was 89.
Eighty-nine!
From then on, there was no more age classification for me personally.
Just categorisation: Being open, life-affirming for new things and for changes in life. Completely independent of age in numbers.