Male here, married 20+ years.
Befor I knew my wife....early 80s, worked at Kamrt, about 150 employees. I knew of at least 15 of the gals that were "open for fun", some were married, all ages.
One was into mfm and more, she liked going to a certain guys place, he'd have another guy or 2 over, she'd get fucked all night, she was about 30. Different gal, early 20s, didn't date but "visited" a married couple quite often, they were 50-ish. Often overnight. Another group of co-workers often went out after work, 4 guys 3 gals, they'd end up at someone's apartment for sex fun together.
Out of town sales reps would visit the store either weekly or semi weekly. The female reps all had a guy they would stay with and not spend their hotel allowance. The men reps would have one of the store employee gals visit his hotel.
The security guy, really cool guy, bodybuilding type. He had an ongoing deal with the HR gal, he was 40-ish, she was 50-ish and not so good looking but he'd spend many nights at her place. He also fucked many of the younger gals at the store sometimes at her place with her involved.
Was very, very common.