Would a fisherman stop fishing after he caught his first fish or a hunter put up his rifle after he bagged his first piece of game? Most of us guys enjoy the hunt, although sometimes we are disappointed when we get the prey and realise that actually we should have just stayed with what we already had captured back home!
I feel wives automatically create openings for mistresses. Humans are domesticated animals brainwashed/conditioned into strange unnatural behaviors that ultimately profit governments and religious institutions, pharmaceutical companies, therapists, counselors, home builders, craft stores, jewellers, attorneys, minivans, SUV's, toy stores, movie theaters, etc., etc. Most men and many, many women both cheat time and again...I think it is really a matter of opportunity really and coming clean about it. Women are hardwired to seek "better providing" mates (revenge sex) and men sexy, willing bed friends. Marriage feels to me like lots of power play while playing house and roof forever. I don't see the "love" in it. In many ways it feels as if we are still living in a Victorian Age but with the mainstream acceptance of porn and adult entertainment in a parallel realm as the norm. I don't know if this isn't true in parts of the world without vast media reach. Tribal societies have different ideals. Hmmmm. Humans in the West would go far if they were honest with themselves and each other.
I think it's a matter of opinion. I believe in monogamy and am typically someone who would consider something more if I wasn't satisfied. However I am happy in the position I am in and would never risk losing it over other "relationships". I found the right balance; but it took years to find this person and never considered entering a marriage with someone who i knew I would eventually lose interest in. I think for each individual it takes someone out of this world to not only stay loyal but truly comitted mind, body and soul. I am filled with 1000 personalities so maybe that's why we're happy too haha! To each their own.