I recently visited my friend from our programming club who saved these letters and was reminded a couple people wrote additional angry letters years after paying for the shareware. They demanded support in return for their one payment. (Of course, not only had I moved on to other projects, but I had long sold the type of computer the shareware was created for!)
So I learned early on that people unreasonably expect support for no additional cost. Or they believe the amount they paid is for support in the future, not work done in the past. It doesn't work that way economically. A constant flow of additional money has to come in the door to pay a team to do the actual support.
AFAICT, the only feasible models for supported software seem to be subscription, microtransaction or advertising. Any one-time-up-front price means it's abandonware. Which is fine for some types of software, of course, but probably not as often as users expect support.
