I didn't co-habitate with either of my Mirage GFs. With the first one, I liked the sex but I didn't think she and I were on the same page a lot of the time. With the second, I felt the same.
But if you aren't married and have been around the block a few times, you realize that marriage is not a requirement in many cases. You can just hang out and enjoy each other's company, and when things get a bit weird, you or they can go home.