Originally Posted by
FutureYesterday 
How long will it take for him to go back?
To clarify -how long will it take him to go back to what? If you are asking how long it will take him to go back to being able to drink safely, that will likely never happen. Once you've crossed the line to the extreme levels of alcohol abuse he has, you really can never go back. I know that's not the answer you'd like to hear but it's true in nearly every case.
He could certainly choose to abstain completely too, so it's not as if he doesn't have a choice. But he cannot choose moderate drinking anymore, that's simply not an option.