Welcome back! You have good timing, since I'm in the middle of a version change.
A premium version will actually be back next week. It's not nearly as simple as it used to be, but I'm making a second product page to house a full-price version of the game that will stay up to date with new versions forever. I'm planning to send coupon codes out to all the people who spent money on Itch so they can put that towards the new premium purchase (and it'll be on steep discount for the first week that it's visible).
I'll be posting up a devlog here when everything shifts over. All of the information for the various versions and payment options will be described in more detail there.