I've seen my wife have sex with every one of her lover's over the years, but not everytime. My wife has been with seven other men, and all but one were long term relationships. Five of those seven were (still are) good friends of mine. Early on in each relationship I was there to witness her liaisons, but as the relationships grew, she would spend more and more time with them alone. I would say on average, that when she's with a long term lover, she sees him alone about 60% of the time, and allows me to be there 40% of the time.