In a relationship is a maturity intellectual and developmental gap supposed to widen as you get older?

From what you've said it sounds like he's an alcoholic. Alcoholics and other obsessive-compulsive people stop maturing due to the nature of their illness because they're hiding from reality. It's unfair and ist to ume that it's a gender difference. I've met plenty of immature women my age and I'm 49. I've even dated women a few years older and I was still more mature than they were. In this case I'd say his drinking is the main factor hindering his maturity. It probably isn't helping his intellectual capacity either; it's a wel-known fact that excessive drinking kills brain cells. If you can't live with it I'd say you need to move on, because he won't change unless he wants to.