Of course!
Hell, I've woken up when my wife had tried to wake me up for morning sex and she finally just started on her own. Sometimes the bed rocking enough gets me up.
Many times I don't stop her, and I even fed her my cock. Another great thing to do while she's rubbing her clitoris on a pillow or something else is to put my pelvis under her breasts. Her nipples get stimulated inside of my thighs, and she often sucks me as well. I'm seriously considering buying her a Symbian for Christmas. A lot of women get off far better with that than intercourse or a lot of other ways.
Some men would think I'm crazy, and that she might not want me afterwards, or might not give me intercourse anymore. Get real, it's more than just the intercourse, and my wife is always offering up her breasts, mouth and vagina whether she gets off or not. Besides, having intercourse while she's in an extreme quiver because she just went on the Symbian is my idea of an ideal mission.