Take college classes, consume online programs, eat at different restaurants, build robots, build furniture, volunteer at foodbanks, teach numerous subjects, play sports, attend social events, play chess, visit different cities in one state, and more.
Model railroading though it's kind of too messy, buy a bunch of LEGOs, and buy Neopets to restore it to its former glory - work on my golf game and go to the driving range every day or so and fix all my clubs, fix up old bicycles, learn welding and mechanics and restore old trucks and cars.
I watched a TV documentary series recently called Orangutan Jungle School where they take care of orphan orangutans. I want to travel to Borneo and apply to be one of the caretakers and be with baby orangutans the rest of my life. Yes you would have to have some education and know Indonesian but that's my fantasy dammit!
As you get older being comfortable is very important - and hobbies (for me anyway) sort of fade into the background.
Nowadays I like music - which is easy because it's free on the internet, rare books - which is good because I always sell them for much more than what I pay for them. I can enjoy them for a while then get rid of them. And travel - which is made much more comfortable by selling the books.