Most of the folks who initially asked for a self-hosted version wanted a way to pay once and then know their deployment could operate offline indefinitely. I hoped there might be a bit less piracy risk that way too.
If others would be more interested in a recurring model for self-hosting though, I'd definitely consider it.
For pricing models, JetBrains (PyCharm) has a nice setup, although it could be more user friendly. After 12 months of payments you get a perpetual fallback license[0].
The more user friendly version would be getting perpetual access to the current version of software after 12 months of payments, rather than the backdated version. But I understand their reasoning.
0 - https://sales.jetbrains.com/hc/en-gb/articles/207240845-What...
But I do wonder if/how that might change with an alternate licensing model.
In the examples you've heard about, do you recall where the most significant support costs oftened stem from?
At this point, I can barely imagine trying to create and maintain a cross-platform self-hostable product the old school way.
We also certainly hear about companies or individuals looking for an easy way to send money for FOSS projects they rely on, so hopefully it works out for you!