Well I have gone 15 years without a shave then I needed to shave off my peach fuzz xD after that, most was maybe a month. I refused to shave during exams while in college, I called it my exam beard.
I've had some long periods of sporting a full beard, but even then I shaved my upper cheeks and neck and tried to keep the lines neat at least every couple days. These days its just a goat and a stache. 48 hours is my typical limit to go with not shaving, and I typically shave every day. I've gone well over a week while in hunting camp in the past. I try to avoid going that long, no matter the circumstances now though.