Not as much as I should honestly. I'd do it however much you feel is necessary. Too much won't hurt him. I'd just do it when I thought about it. Even if it's not every day. I usually do it in the middle of the day when he wants to play with his activity mat. But usually I just do it once a day.
He will just start getting restless and fussy. Or will lay his head down and give up lol. But more often than not he just starts getting fussy so I flip him back over into his back. Usually anywhere from 5-15 minutes is how long he's good for.
My son holds his head up and pushes his feet. Up. How do you no he had enough ? Crying ? I'll deff have to start doing it with him @jacesterlingsmommy I mean he lays on me with his belly but I know I got to try to let him lay on his own ish lol. My son is colic so he wants to be moving constantly