Personally, I get off on seeing that look of pleasure in a woman's face.... I see it more as a, "if you fall of the horse..." kind of thing and I can say that I have actually gone long enough to get cramps in just about every muscle that can be involved in pleasuring someone. Be honest about it and on any given night, turn it into a game to see if you can find something that eventually works "Ok, tonight...if I can make you cum, I get the dry side of the bed" (or whatever...)