Depends on the spouses. If they are okay with it, and if actually makes their marriage work better, who has the authority to castigate them? Keep in mind these are all adults in their 50’s, not young couples in 20’s or even 30’s raising young kids.
If all 4 adults are happier because of the “consensual adultery”, who appointed anyone the moral police? Life is too short and full of ups and downs, to not seek maximum happiness.
That is quite disgusting and completely morally depraved, to put it mildly.
Sick and disgusting.
“who appointed anyone the moral police?”
Pretty sure it was God.