Imagine that you have an adult child who lives with you in your home (defined as the least or mortgage being in your name, since I know somebody is going to want to try to sound smart and derail this by saying, "It's my child's home, too!") Are you alright with your child having overnight guests of a romantic nature? How often would be too often? Does your answer change if these guests are somebody with whom he's in a long-term relationship vs. one night stands with different partners?
Does your answer change if your child is still legally your dependent (think anywhere from 15-17, with any partners being of an age that won't cause statutory rape laws to be in effect. Also pretend that the partners' parents are okay with sleepovers)?
Inspired by seeing my neighbor's girlfriend do the walk of shame* almost every morning.
*I make my own definitions and I would definitely be ashamed to be with somebody who talks to me like he talks to her.