I think it could be that we all need a bit of variety in our lives so we don't get bored. As much as I enjoy fillet mignon, for example, the novelty would wear off if I ate it every day. I still want to eat it, but maybe just once a week cause there are other good foods out there, some just as good, and the ones that are less good will make the fillet taste extra special when I have it again. Maybe for some the novelty never wears off. But if it does a little, I think that it is better to find a solution. This doesn't mean stopping the marriage, because for some people, no matter who they are with, need a bit of variety after awhile and they may be satisfied with their marriage, other than the lack of variety. Maybe your "married man" example will become happier and more relaxed as a result of his ventures and see his life from a new perspective. At least this one has taken the first step. I think that institutions like marriage, the law, education, the media, the government are denying the truth: that it is perfectly normal to be attracted to many, many, many members of the opposite sex, not just one's spouse. And as a couple get older together, I am sure that one looks at their spouse as less and less a "hottie" and appreciates them for other qualities. So the 70-year old or the one who has been married for 15 years will still find the younger and the unknown more physically alluring than the older and the familiar.