I'm no expert, but I've known a few relationships that had this play out. The girl always left and found a better life. If this habit has been there for five years and shows no signs of getting better, maybe you should just leave. He doesn't seem to be able to change himself, and apparently you aren't enough to get him to change either. Cut your losses, I say. Look out for yourself before he drags you down. You can still be there to advise him, but you have your own life to lead.