Personally, I have atleast 5 or 6 that I rotate....Its nice to have more than one because some are busy some nights and some have boyfriends occasionally.
It works out fine for what we want. And nothing more. I'm probably a bastard for this in some way, but they don't want anymore than sex, and personally, I don't either. My only vice is they have to be tested for VD so we're all still clean afterwards. Of course we use protection
It works.