I'm going to have to step outside of the theory, although I completely understand Michele's point, and think it is probably true for most people.
I married the first time at 16 years old. I was completely clueless and definately didn't marry for love. As time went on, all of the signs I should have seen early on became a pattern of him drinking and being abusive. I attempted to make it work, but there was never going to be any happy ending there.
My current H was married twice before, briefly. Despite birth control, he had the misfortune of getting a woman pregnant. She wanted to have the baby Because he was in the military, he was able to provide certain benefits, including free medical care for mother and baby if he married the mom. I knew them at this time (strange story--my first H and I were their next-door neighbors and friends) They definately did not marry for love and the marraige died a natural death.
Second time around, he again, despite birth control, got ANOTHER woman pregnant. Yeah, yeah, I know.... SAME story, he married the woman to provide for the child, marraige died a natural death.
By this time, he'd had enough of the unplanned babies and got "fixed".
He and I remained friends. His wife #1 and I remained friends. I lost track of him for a couple years and ran into him one day out shopping. We exchanged phone numbers and planned to get together to catch up. As we walked away, my son asked me "who was that guy?" I said, "that's an old friend of mine. I can't explain it, but I have the strongest voice inside me saying I'm going to marry that guy!" It was so weird, but 6 months later, we were living together and have raised my two sons and his two sons together.
Basically, it was the first time either of us actually CHOSE to be in a relationship and went into it with full knowledge and intent.
Despite the difficulty we have had the past two years, with him in full-blown MLC and having an affair, I would have to say even now that we are much happier that in previous marraiges. In fact, now that we are addressing some of the cracks that were in the foundation of our relationship, we can both picture ourselves growing old together.