when I have long sex (45 min - 1 and half) I have to pass a certain boundary of physical pleasure, if I don't come before I pass the boundary than I can go nearly indefinatley and come once I want to (within 30 seconds or so of me deciding that I want to. It can take anywhere from a few minutes to twenty minutes before I go pass the boundary for a lack of a better word for it, and probably half the time I have sex I cum before getting to that point.