Most devs either offer a "buy once and always get the newest version" deal or only allow you to pay on patreon. There are definitely games where I purchased the paid version on itch years ago and can still access the current paid version.
Ahaaaa!! I see where I messed up! This was my bad homies! I figured out where I made the mistake so people should be able to get future updates for free once they've purchased it once.