I was happy recursively paying for Pycharm even sometimes I didn't use it for months. I see many people do that with Adobe products. If I had an option to pay Postgresql, Flask, VSCode developers a small amount every month , I would be happy to pay it.
One thing I would love to see is to have an option to pay the OSS developers. There works are worth not only donations but payments. In the other side, I've seen enough higher managers refuse to use OSS. Their reasons are really understandable: "Who I'm gonna call if the software has some bugs?". Contracts, and sometimes expensive prices, are what they need before invest in new softwares.
So how these contracts should work in a Patreon-like site? If I had implemented the site, I would shamelessly copy the Patreon's tiers model. The cheap tier would require the developers just keep doing whatever they are currently doing. More expensive tiers would be for support contracts. I pay this developer for that project, and I'm guaranteed that I'll receive email support within 24h. If I pay more, I may have access to phone support. What kind of supports and how much are they worth is the OSS developer's decision.