I decide when my slaves get to cum, their cock belongs to me and I will drain as much or as little of spunk out of them for my perverted experiments as I like. He can't reach his erection anyways, with his hands tied. I love to tease him and make him very desperate, make him rock hard and let him edge until I decide to extract his sticky, white fluids with my latex gloved hands. Of course I will ruin any of his pleasure. After all he is just meat to milk.