I think it depends on the service you are providing, but the only way to tell if it is viable for you is to test it out. You could try two approaches to test it

I think it depends on the service you are providing, but the only way to tell if it is viable for you is to test it out. You could try two approaches to test it out. 1) reach out to old clients and see if they would be interested in the recurring fee 2) When you are negotiating with a new client, bring up that they could also just pay you X recurring fee instead.