Before my wife and I were married she had dated quite a lot. It was not surprising to me, as she was a rare beauty with a really pleasant and engaging personality. Men just liked to be with her, and she liked being with men.
Somehow I managed to win my way into her heart, and we were subsequently married--and have been for many years now. But I was always fascinated by her experiences with other men and would often ask her to tell me about them when we made love. Eventually I found myself drawn to the idea of seeing her with another man. I knew one of my closest friends had always wanted to bed her, and approached him about trying to seduce her. At the same time, during pillow-talk with my wife, I began mentioning how much I'd enjoy seeing her pleasuring my friend. She proved reluctant for some while, but eventually agreed to ...... with him. That began an on-and-off series of trysts that lasted a little over ten years until he moved to the West Coast.
Meanwhile, about halfway through that relationship, another of my close friends became aware of all this and asked me if he, too, might avail himself of my wife's pleasures. Much to my surprise, while it had taken me two or three years to persuade my wife to ...... with the first friend, she proved eager to bed the second at the first suggestion. That began an affair that has endured to this day.
For awhile then, about five years, she was fucking them both, not to mention me--successfully juggling three men's sexual needs Not every day, mind you, or even every week, but often enough that all three of us were pretty happy with the state of affairs. So yes, it can work, and I'd say that the key to success is making sure everyone involved is getting something out of it he or she wants or needs.