I don't think there's an ideal number of revisions, and most creatives would be happy with one round, hit that home run, and appease all the stakeholders right out of the gate. But I think it's an exercise in being extremely collaborative with your production teams and managing scope, and setting the right expectations with clients.
There's certain changes that will be a no-go because they're massive global changes to a piece of creative, or to the fundamental creative roots of a campaign, that can't be touched unless you're doing a brand new project, where you're scrapping this one and doing something new.
I think each revision needs to ladder up to the creative brief that was agreed upon, it's just being cognizant of which changes are acceptable and being collaborative with clients and negotiating all of that through.