I would go four, five months between haircuts. The surviving photographic evidence suggests that I could still carry off "tousled" in my early thirties. These days the transition from "could perhaps use a haircut" to "seedy" occurs much sooner after the last visit to the barber, and over the course of maybe 48 hours. As my old man used to observe when, back in my teens, I whined that it was my hair, "Yeah, but you don't have to look at it." Spare the sensibilities of your family and colleagues even if they don't return the favor. Anonymous passers-by will thank you.

cordially,