FWIW, I have paid for OF subscriptions for three providers *after* I saw them. It adds a lot to porn knowing you have been with the person and might again.
I've also paid for a subscription for a burlesque performer I was attracted to and wanted to support.
In each of these cases the performers eventually stopped posting on OF and I dropped the subscriptions.
I do like the idea of paying for a month before seeing a provider to get a good sense of their vibe, etc though I haven't done that yet.