I can say for the woman who do this is a stupid thing. But many did it. I doubt if these women really have peace of mind and comfortable with the arrangement. Get a divorce, free yourself before doing silly thing, because this thing will never exist for a long time.  But i have a "Big Question" why are they doing it? Is it for pleasure, money or revenge?

"There's nothing we can do to change the past, if it teaches  you a lesson profit from it then, forget it."