I dunno, I personally could never stomach a monogamous relationship.
Hell, I really don't have an even slight interest in cheating either. I mean, I get the whole concept of things getting very mundane and similar, and other women possibly representing something exciting or varied...but it's truly not worth it.
I'm probably extremely naive and romantic, but I've always had this concept in my head of what a relationship should be. A kind of symbiotic, cohesive unit with an assurity and perspective of an everlasting system of mutual care and support.
And that, to me, is worth way more than any other connection - physical or otherwise - could offer.