Sub on his knees with his balls chained behind him has his cock milked and orgasms ruined 4 times in a row

My sub kneels on the floor, naked, with his balls chained up to his waist belt to keep them tugged upwards (makes the almost orgasms extra intense). I milk his cock from behind with a lubed hand, slowly and methodically. When the cum is about to flow, I stop perfectly to ruin the orgasm while squeezing his balls. After the first ruin dribbles out, I resume and quickly tease out 3 more ruined orgasms in succession. One after another, I ruin them all – his cum just drips and spurts out uselessly each time. He’s left on his knees, balls aching and cock throbbing, having endured four back-to-back ruined orgasms. I, of course, am delighted and make sure he knows what a good empty cumrag he’s been.