I have faked on occasion. Condoms make it easy. You just go through the grunting, the "oh baby", the "fuck yeah, girl" and then fall over and say that you came to quickly to get the condom off (in case of a facial lover) and then you quickly dispose of it. Seriously, a few years back after a long flight, and being away from the ex for a week, she was insatiable. I just wanted sleep. So I perfected my act. I have used it a few times since when the booze wears off and you realize that the pick-up was not so hot afterall.