The first "real cover band" I joined, at the ripe age of 26, had a no mixing alcohol and music policy. Though everyone drank socially, never when practicing, rehearsing, or performing. Wanting to fit in, I went with it. This band had a large bar/lounge/club following and played out literally every Friday/Saturday night, so I felt lucky to be part of it. Once, for the heck of it, at the end of the evening when we already had the audience eating out of our hands, we all had a beer between the last sets (on empty stomachs at that point). It was SO strange. We didn't crash and burn, but it was disorienting enough that we never did it again.
That alcohol policy stayed with me for many years. Later, I realized that a beer (with a little food in my stomach) didn't really do much harm, and I could have a few if I spread them out and drank lots of water in between.
Everyone's different. I know people who have some very odd and atypical idiosyncrasies pop up on stage after drinking; they should avoid it or cut back. I know some people who drink routinely through the course of the week, when they practice at home, at rehearsal, and at the gig. They're pretty steady. However, I think if you take that mentality just a step too far you may be a functioning alcoholic.
