I've been observing my grandmother who just turned 100 in May. She has always been a good seamstress and even now at her age she is part of a quilting group, making small lap blankets for people in need. I think it's part of what has kept her going to 100! It gives her a purpose for life and she feels like she is still making a positive contribution to society.
I'm trying to find a hobby that I can enjoy and keep doing for years to come. Can anybody think of other hobbies that are sustainable to old age?
I think that making music is one of the best hobbies there are out there. And with these kind of hobbies, the longer you are doing each hobby, the better you will be at it. That means if you start now, later on in life you will be very skilled at performing music. All you really need is a musical instrument, and it can be bought for pretty cheap nowadays. If you want something fancier down the line, as you will probably want to after you get better, you can make that investment too. But you don't need that much to start with, and it will get better the more you play.
I think that active hobbies are great too. If you pick up running or a sport, you can do both stay healthy and keep yourself occupied. There are so many great hobbies out there that you can have your pick of things you want.
Probably anything that has no skill-ceiling and serves some purpose in the world - doesn't benefit just you but also other people by one way or another, even if it's something that can lightly inspire or motivate people around you. I think everyone should do somethng like that, too many people are caught in a 9-to-5 job that they hate and getting drunk or playing video games after.
Aquarium fishkeeping can be a very rewarding hobby, and you can get as deep in as you want, from a small betta aquarium to a full fledged reef system. Just depends on your money and patience.
My other easy to get into hobby is writing. the more you do it the better you get.
How abotu learning how to cook well? I would describe it as a hobby if you really get into it. It's something that you will need to do forever, so it would be good to get good at it. You can make lots of interesting recipes and foods and share them with people. It's a hobby that benefits a lot more people than jsut yourself.