My dad always taught me that a man should get his hair cut often enough that his friends and coworkers can't tell that he needs a haircut. He said you need to present a consistent, professional appearance when you're out in public. He said you don't want someone to be standing within your personal space and thinking, "This guy needs a haircut!" To that end I always get my hair cut every 2-3 weeks depending on how "tight" my appearance needs to be. My own standards for when I need to get a haircut always seem to be stricter than those of the people who know me. I'll often tell someone I'm going to the barbershop on Saturday and the response is usually that I don't look like I need a haircut. Exactly. If I look like I need a haircut I've obviously gone too long without one.