My wife prefers long term relationships over one night stands. She also prefers to have sex with men she already knows, is attracted to, and feels comfortable with. Because of that, out of the 8 long term sexual relationships she has had with other men over the course of our marriage, 6 of those men came from our close circle of friends (including three of my best friends, one who was bestman at our wedding)! All have known upfront that I am aware and okay with them having a sexual "friends with benefits" relationship with my wife.
Pictured, four of those lucky friends...