In my first marriage we played around a bit, threesomes with another girl then another guy, dates with people we wanted to fuck. While the marriage did not last the sexual adventures were not a reason for the breakup.
Some years later, in my late forties I remarried a girl fifteen years my junior. She was 5'6, blond hair, 115 pounds with 36C breasts. She had been in San Francisco for the Summer of Love and was very sexual. While I had made love to a dozen women she had racked up over fifty lovers. We had sex on the first date and almost every night for the next several years.
Then years of smoking and high cholesterol started slowing down my responses to the point that an erection became an unusual event. We still had sex. She did not climax often from intercourse so I would end up eating her to a finish. I could tell though that she missed my cock.
We were into role playing, going out on dates with each other or meeting in bars with me picking her up. One day I brought up the possibility of her taking on a lover for regular intercourse. Over the next several months we continued the dialog and she slowly came around to seeing the possibilities of this type of arrangement. She admitted that she would enjoy have regular sex once or twice a week. I told her that I would love to watch her at least once and we agreed to consider that.