I don't know if there is an accepted standard recommendation but my surgeon said that I should go every year for one but my GI said that they weren't necessary. Go figure, I would have thought it would have been the other way around with the GI saying every year because he would perform the scopes.
I had my j-pouch because of UC, if I had my j-pouch due to cancer then my GI said that I would need closer monitoring.
Scopes are quick and easy, you can have them with or without sedation. I'm planning on going every 1 to 2 years for a scope.