My wife and I have been married for more than 20 years, with all but six of that being happily non-monogamous (the six being before we were non-monogamous, and those were good years too!).
When I was much younger, I would get jealous easily. I was even jealous at age 20 about a girlfriend of mine seeing a male gynecologist. Now, I "suffer" from compersion. I thoroughly enjoy my wife having sex with other men. I love watching, love participating, and love her coming home from solo dates. We have remained exceptionally close, and it's all been very much a positive in our marriage. I wouldn't have it any other way.
We do swing from time to time as well, and I play solo from time to time as well. All told over the years though, it's been 10:1 my wife getting to play, much to my enjoyment
She's had some boyfriends along the way, and gotten to have sex with some truly great guys. It's been a heck of a journey.