I agree with the "enough work" aspect. I stayed and was monogamous with the same woman for 27 years.
One thing for sure: in my case, the monogamous marriage arrangement provided for the most in-depth personal growth of my being. It was the perfect device to teach me some of the most profound lessons in life. Although that relationship has passed, and I am in the "prefer to be alone than to start over with a new one(s)" stage, I am thankful for the many doctorals I have received through that school.
It was the concern for hurting others, the trashing of my conscience (I'm a terrible liar) and the probable negative financial repercussions that kept my fly zipped.