I've had to shave for as long as I can remember... Think I started when I was 13-14 (can't remember exactly that far back)... I do know that I started growing a beard as soon as I got to college. But since I was in Georgia, and then Florida (when not in college) it wasn't wise to have a full on ZZ Top style beard going. Still, there were plenty of times I let it go longer.
These days if I go more than about 4 days between shaving (I don't like to shave until day 3) it gets long. Chews up blades faster, although the shave feels smoother. Plus, since I'm also shaving my head (not as much hair up there as you might think, maybe) there's more work for the blades.
Must be my Russian and Polish genetics giving me the good beard, but also taking it from up top... Then there's age putting more hair where I DON'T want it...