Game companies implicitly do this, throwing out old versions of their code (sort of). You make a game. Ship it. Start on a new game. Your previous game is now sort of a practice run for making a new game from scratch. Continue, ad infinitum.

It's weird: you rarely have to maintain something for 20+ years, and you get to always improve and iterate on how you did things last time. But, are you training yourself to write hard to maintain code, since you don't really have to maintain it past a certain period? Or does the learning-from-iteration actually make writing-maintainable-code easier?

I know some people do keep developing their games for decades, look at Dwarf Fortress, I'm just talking in general.