I've got a few different perspectives on this, based on both personal experience, and the experiences of people I know. One....two good friends of mine from college got married, and decided 15 years into their marriage to open it. The wife ended up falling in love with her boyfriend, and she and her husband got divorced. He was pretty bitter about it.

Two--my middle step-son has been involved in a polyamorous relationship for years. It's him, another guy, and a woman. They even all three own a house together. They kept things just between the three of them for a long time, but have recently "opened" the relationship, and are now dating other people. In fact, my step-son and the other guy in the relationship are dating sisters. Yet, the original three still maintain their commitment to each other. It's interesting, but it seems to work for them.

Third--I wrote something kind of on this subject early on in my Steemit career (which, granted, is just 3 1/2 weeks so far). I've encouraged my husband to have sex with other women almost from the beginning of our marriage. It's just something I was always okay with from the start, and, interestingly, his second wife (the one just before me) had the same arrangement with him. I don't know. Maybe he inspires it in women, or something.

I wrote about my reasons for encouraging him to have sex with other women. You can read about it here:

https://steemit.com/anarchism/@stephmckenzie/getting-girlfriends-for-my-husband-why-i-encourage-him-to-sleep-with-other-women

I also want a divorce, but that has NOTHING to do with the "encouraging him to have sex with other women" thing. That was perfectly okay with me, and even something I wanted him to do, LONG before I became dissatisfied with being married. Oddly, part of the reason I no longer want to be married is that I can't stand dealing with his insane jealousy anymore....and I've never even kissed another man in the 20 years we've been married. Yet, he's always accusing me of having affairs, and I've never done it. I can't get him to believe me, though. Paranoia is part of his mental health diagnosis. The jealousy and emotional abuse that comes with it has kind of turned me off of the whole idea of marriage in general.