Quantity makes a huge difference. I'd do a little "H" (nasal cavity, no needles for me) before the gig, then maybe another one midway. Then the band and I would smoke a joint before the gig, and one between sets (this would be at one of those 6 hours gigs at someone backyard barbecue, or wedding reception or something). And nurse maybe 4 - 5 beers throughout the night. Nothing really excessive (by my standards anyway).