mkr86, were you thinking of having children at some point? If so can you see yourself having them with him? I think you may be right that he will use in some way indefinitely, but what does that mean for your future? There's always the possibility he'll ramp up his use, as there is with any addict.
I just don't want you to get to your mid-30s and say you regret not having a 'normal' relationship where you would feel confident about raising kids. It's not for any of us to say what you should do, but if you stay, at least make that decision having thought through all the consequences.