Thanks for sharing your experience! I've been thinking about adding a credit system to my PDF generation product [1], so that people can perform one-time batch jobs, or for companies that have very seasonal workloads. I agree that recurring revenue is the best, but there's also nothing stopping people from suspending their account if they don't need it anymore. I haven't had anyone do that so far, so maybe this would be the wrong direction.

[1] https://formapi.io