I read how much exercise all these people say they are doing, and yet I look around where I live - a lovely coastal area in Australia - and see a lot of older folk doing not much more than a slow stroll. Reading what all these people say they are doing makes me feel completely overwhelmed!
I'm 67 and I do the supermarket shopping, walk the dog twice daily, do the housework, wash the car, look after a tiny garden. So far I am managing OK, but I do get tired more easily than I used to.
I also just enjoy being home watching a movie, reading, listening to music.
I go to a cafe to meet a couple of friends regularly, I chat with the neighbours, I go to the cinema quite often, love reading and movies and opera, and am on several online forums.
I honestly think it's not about exercise - although sitting all day is a disaster - but what someone else said here, (sorry I couldn't find them again to quote them) -keep moving and bending - you need to keep pulling up the weeds in the garden, going up and down the stairs, go for a daily walk with the dog - and keep interested in things, have some hobbies, use your brain, and above all, keep a sense of humour!
At least when your body starts to give way a bit, this way you'll hopefully still be someone who is pleasant to be around.