Hello! We try to follow a similar model as Patreon, with monthly updates that are charged separately (tho this is not always the case for Itch, as we have a different standard for the amount of content we have to develop before posting a new version in here). For version 3.30, we might post some updates (possible fixes, extensions of existing scenes). But when the new version is ready, with more content, a new page is created on Itch, with different files uploaded and ready to purchase.
I hope this solved your questions and thanks for considering supporting the project! I hope you enjoy the version you decide to get! ^_^