Depends on what "sex" means. If we're talking about intercourse, I did without it 17 years before losing my virginity, and I've gone without it for several years a couple of times since.
The longest I've been without an orgasm since I had my first one at age 11 has been about 10 days, on a extended backpacking trip with a male friend of mine. I've had many similar "dry periods" of a few days on other backpacking/skiing/mou ntaineering trips.
But otherwise, I seldom go more than 24 hours without cumming!