Not to be a wet blanket, but for a lot of people the answer is "none at all." I speak as a reformed alcoholic. 25 years of drinking, perhaps half of that knowing or suspecting I had a problem. Very roughly, about 1/10 of drinkers are or will become problem drinkers. "Alcoholic" doesn't have a precise definition, but something like....when drink has thoroughly f***ked up your life, and often damaged you and others. Unlike many problems, there is no way to know in advance who'll become an alcoholic. It's a self-diagnosis (at least in AA). Recovery is possible. Ever drinking "normally" isn't, as far as I know.
-- Pedorrero, who had drunk enough probably for 3 or 4 normal lifespans, and thus should be in the peak of health...?