I can go that long in between drinks. I really don't enjoy the lingering effects of drinking heavily, so I usually only have one drink every once in awhile, like a single margarita or a beer or a rum and coke, usually no more than once a month.

I don't usually get people questioning my lack of drinking, but then again I am in older social circles now.

You can also just say you're on a diet and don't want the extra calories, that's an easy way to deflect it.

There was this one girl I dated that was completely baffled by this, though. She only got one night a week completely to herself (single mother, had a babysitter), so she didn't want to waste it and would drink harder than most people I've hung out with, even when I was in college. At the time I went along with it and drank a lot more than I really wanted to. I'm glad I'm not still in that situation, though.