When I’m paying attention, around every two months. Or at least, that’s when I start thinking “you know, I really should get my hair cut…” And I get somewhere between a trim and an inch off.
About once a year. I have waist-length hair, and the abovementioned Samson complex. I should get it cut more often to keep it from looking tangly. I cut about an inch off it last night, after giving a friend his once-every-six-months haircut.