My boyfriend drank for 40 years. He used to drink a fifth of brandy every day. When that no longer provided the desired numbing effect, he moved up to the largest size bottle (a half-gallon I believe) roughly two years ago. He died of alcoholism seven months ago.
I think the timeline is different for everyone. What helped me prepare myself for the inevitable and determine what stage of the disease he was in was conducting google searches on the terms "late-stage alcoholism" and "end-stage alcoholism."