I think that age as a number is not nearly as important as health. You can be in poor health and be pretty miserable at 40 or 50. If you're in good health, you can enjoy things into your 80s.
“I used to smoke cigarettes, ten a day, but gave up when I was 28. Now my vice is several cups of coffee a day, which isn't great if you're prone to weak bones as I am, as caffeine can leach calcium.”