This is one of those moments that makes me fall in love with the internet all over again. I've thought about this idea (without knowing there was a term for it!) wrt aging in real life. So many people seem to become increasingly caricature as they get older. The guy who likes woodworking and European travel becomes the embodiment of woodworking and European travel. It's all he talks about. His kids roll their eyes at…
From your own perspective, you have less of an interest in pursuing entirely new projects because the horizon of good experiences from those gets shorter, and as you have said you also gravitate more experience towards the things you have pursued, which unlocks other experiences on its own.
Orson Scott Card once said that Asimov was one of the few writers who kept improving in old age, because most others would fall into the trap of indulging in their eccentricity and assuming that the image people had of them was already set in stone.
I'd say it's helpful to always keep a slight distance, even from things that become increasingly foundational to your life. True bitterness comes when you cease to believe that new generations are actually capable of enjoying their things the same way you did yours in your youth. As long as you don't lose your capacity for theory of mind or refuse to believe that time goes on, you'll be fine.