Cohabitation isn't “allowed” so GF and BF shack up in GF’s or BF’s dorm room every night; much to the chagrin of the roommate who now has to share a small place with TWO people who do naughty things to each other.
This happened to me in the USAF. Except they didn't alternate, it was my dorm room every night. They got married and had to wait a month for off campus housing, so I was defacto living with newlyweds with my bed not ten feet from theirs.
Yeah, unfortunately I had some of those experiences, too.