Could a public relay utilize this to request donation on occasion too? 🤔
Testing one-click relay renew popup flow with nostr:npub18kzz4lkdtc5n729kvfunxuz287uvu9f64ywhjz43ra482t2y5sks0mx5sz (NIP coming). If your paid relay subscription has expired, the relay can send this popup to renew your access.

Discussion
Sure. Just don't annoy your users :)
Right... that would be on relay operators to choose the appropriate frequency without chasing off their users 😅 ...on first connect, then once/month or so (suggestion for any operators out there😉)
This is awesome 🚀