FWB is great until you care about the chick. I had a few that came to a crashing halt when I got too into the relationships. With some distance I'm starting to see that any girl who is cool with FWB is a little off and pretty slutty. Have your fun but keep your emotional distance; these women don't get close to anyone. It's their character flaw, and not your problem. You are free to walk away... and do. They aren't used to guys who don't beg them to stay.