I know it certainly CAN improve--the mechanics of it should improve within a few months. But the most important sex organ is the mind, and if he is white-knuckling it then that is likely to be a significant contributor to the problem.
I dunno--life with a miserable "dry" drunk can be almost as bad as living with drinking. Obviously he isn't likely to risk anyone's life behind the wheel (unless he is prone to road-rage, which wouldn't surprise me), but who wants to live with someone who is miserable all the time?