man marries woman who was a swinger and wants to go back into the life. He decides he can't fight so he decides to swing so hard and so often that she burns out
man marries woman who was a swinger and wants to go back into the life. He decides he can't fight so he decides to swing so hard and so often that she burns out
Not an exact match, but try Falling Off of the Swing by StangStar06.
https://storiesonline.net/s/70831/falling-off-of-the-swing
In this one, she decides that since her parents both had affairs with multiple people and that led to divorce, if she and her husband could separate sex and love (make sex just a purely physical act) they could both have lots of sex but still be madly in love and live happily ever after. This one involves them going to a club where couples can have sex with others. Needless to say, it didn't work out how she wanted.
I just came across this story that seems to be a better fit:
Across That Line
by Longhorn__07
https://storiesonline.net/s/50365/across-that-line