I don't think there is an easy answer to this... It depends so much on the individual and their life. However, I think there are some general guidelines that work in a "most people, most of the time" kind-of-way.
With that said, I think that most severe alcoholics can never go back to drinking. The damage has been done, and they will always have that vulnerability. They may be able to control it for a while, even a surprisingly long time, but, if they go back to drinking or using then they will be thoroughly screwed.
There are people who may have issues that look like alcoholism, but are really different, like ADHD or depression. As those other issues get better, then the alcoholism will become less of a problem. For example, people with ADHD tend to have problems with impulse control. As people live their lives they learn that poor impulse control is, indeed, a real problem and they learn how to get it under control more-or-less on their own. That same lack of impulse control is disastrous when combined with alcohol. But, as their impulse control gets better, their problems with alcohol get easier, too.
Some people simply have had a crappy childhood, and, as they get more distance and grow out of those issues, then their tendency to addiction gets less.
With that said, I think that most severe alcoholics can never go back to drinking. The damage has been done, and they will always have that vulnerability. They may be able to control it for a while, even a surprisingly long time, but, if they go back to drinking or using then they will be thoroughly screwed.
There are people who may have issues that look like alcoholism, but are really different, like ADHD or depression. As those other issues get better, then the alcoholism will become less of a problem. For example, people with ADHD tend to have problems with impulse control. As people live their lives they learn that poor impulse control is, indeed, a real problem and they learn how to get it under control more-or-less on their own. That same lack of impulse control is disastrous when combined with alcohol. But, as their impulse control gets better, their problems with alcohol get easier, too.
Some people simply have had a crappy childhood, and, as they get more distance and grow out of those issues, then their tendency to addiction gets less.