I decided years ago (after having gotten tired of "living in sin") that my next roommate will be a dog or a husband. My building doesn't allow dogs, and I'm not sure I want a husband. I'm old enough that I'm set in my ways and I'm sure that any man in my age group is pretty set in his too.
I think the 'set in our ways' rings true with both genders. It's fun to go out, do things etc with another person, then walk in your home, shut the door and relax. Fix what you want for supper, watch what you want on TV...no worries.
Just the thought of sleeping with another person gives me hives! No, not sex, but trying to sleep.