It is hard to tell why someone is having a hard time finding work. At your age though, it probably isn't the hair. Usually when a man can't get hired because of long hair, it is some younger guy who is either a slob or trying to look like a rock star.
Some people try to change who they are just to get hired but it doesn't always work. I understand how important the hair is to you, so what would happen if you cut it and the situation didn't improve?
I don't know if any manager would even admit to something like that. They wouldn't want to face a potential law suit.
Most people do not stick around any given company for long anyways. It doesn't even matter what their age is. Even the place I work, I have been there 8 years and even manager turn-around is pretty crazy.
To put it another way, anyone from the top down is lucky to last even ONE year in most places, let alone "years".