I agree with the denial. Couple that fact that time builds up more cum and my Master chooses when I am allowed to cum which has slowly increased between orgasms. However as a control for health reasons she milks me on a regular basis which keeps the pipes cleared out. As far as on command she couples that with the humilation and short phrases and only gives me a short window of opprotunity. And of course it is always at the end of my training session that I am allowed to cum. Most situations prohibit me from cumming inside her and I know I'll have to clean it up afterwards. I know that it is for her amusement and strive to always please her. Back to thet original question, yes it is possible to cum on command, but it so much more fun to add a few other triggers in there too.