How Long Can He Last Under My Ass

I brought along a stopwatch to train this losers smother endurance today. I sit down on his face wearing my tight grey jeans and smother him under my ass while stopping the time. How far can I push his limits?! Of course, Ill only give him short rests in between - too short to really recover and get the oxygen saturation back to normal. The slave moans and struggles under my ass as I flatten his nose and smother him, but thats not going to help him - hell endure this training for as long as I want him to!