If you look at the hundreds of reasons of why we don't live long lifespans cutting of the hair is just one of those on the list. You may never know or feel a differance in your lifetime, but the hair acts as an intenna does for a TV. Long hair also creates stronger roots. Not using soap and not cutting the hair may end grey hair, it has for me anyway. The longer my hair gets I do feel better over all, but I will admit long hair is more of a job to care for, short hair needs almost no combing where the long hair needs combed all the time and maybe that is why I feel better. Combing stimulates the scalp which has to stimulate the brain, etc.
Cutting the hair is no big deal, unless your looking to understand the human body and our hair. And who knows if long hair will add a few seconds of life or non at all? I do see allot of men with very long hair, more than I remember seeing in the past, so i think something is up! Long hair also gets more looks, but maybe it is because they think your crazy!