1 If you are sporting a longer haircut and want to maintain it that way, you should get a trim not later than 5-6 weeks. 2  Delaying any haircut for more than 6 weeks would bring about split ends which are unhealthy for hair growth.e fills us in completely on the haircut routine men need to follow: 1  You know you really need a haircut when your hair begins to fall onto your ears and creeps down to your nape. 2  If you have a short hairstyle and want to maintain that, you should get a trim every 3-4 weeks.