Hmm. Well as a comparative child to all the previous posters, I’d say my mental age is around 60. I’m 40. But at every social event, family gathering, employee engagement, I find myself standing with the retirees. The most recent social function I attended had me sitting with an 82 year old man talking about lawn tractors, social security, home repairs and grandchildren, while everyone else played golf. I do try to walk/run about 9 miles a day(but it’s a new endeavor). I can still lift whatever I think I can, although I’m more inclined to seek leverage. I sleep by 9pm most days, and wouldn’t be upset if I could make it 8. So yep...at least 60.