I used to work afternoon shifts and stayed up for hours afterward. At that time I drank about 20 cups of coffee a day and smoked 2 1/2 packs of cigarettes a day. This went on for over 2 years, until I developed serious stomach problems. I'm down to one cup of coffee a day now, and one pack of cigarettes. I had some bad headaches at first when I cut back on the coffee, but they're gone now. I was also very difficult to live with, as my temper was very short. It took about 6 months until my temperment got back to normal.
Walter