Bodybag facesitting

So, I've kept my slave all snug in the body bag. He hasn't managed to wriggle away, haha. With him securely locked tight - save for his face, I decide to make more use of it. I push my lovely, round arse straight into his face. He can be my seat. How long can he stay with my weight on him - taking big breaths until I permit him to breath again. After 9 minutes of sitting and teasing, I leave him alone all wrapped up - ready to return late for more teasing and taunting....