It will progress. Chances are, if he tried to stop bingeing, it would last for a bit, but when he hit it again, he would hit it harder. Alcoholism is a progressive disease. Do not take that statement lightly.
He may be quite young.
If he is driving around with you in this state, I would try to stop allowing that to happen. He will fight for the right to drive when that inebriated. Your safety is at hand.
Also, one thing you can do, if you want to, is to choose NOT to accompany him at all when he drinks. This is an ACTIVE statement. You are choosing not to be around his drinking, to not take part in it with him.
If you drive, you could bring your car to go out together, and after he passes the acceptable drink mark, you could say goodnoght.
He may ask the next day why you left. If you do this enough times, he will realize you dont want to be around that.
Is he abusive when drunk? when Sober? does he make you feel small? Get angry about things other people dont? Is he suspicious? Does he get into a lot of fights when drinking?
Ask yourself. Does his personality change when he is drinking?