Have you figured it out yet? All of these girls have followed the first two lessons perfectly. They slowly built their man up, with enthusiasm and clearly enjoy what they are doing. And look even after blowing their load, all of those cocks are still rock hard. Just as hard as your cock right now.
They are hard, horny and easily ready to go another round. Now, I'm not saying this will happen every time. Sometimes when I have a guys cock down my throat as he cums he is just empty afterwards and too tired for another round. There is definitely a sweet spot, but once you master it you will be able to cum without loosing that urge to do that special thing we were talking about earlier.
Give him another 100 strokes at the medium pace.