We've overlooked a potentially useful discussion in this thread.
There are two practical, and therefore, the only significant reasons for having long hair: Insulation, and aesthetic (not necessarily fashionable) purposes.
Though this is probably not so necessary because people in industrialized society have access to a heat source of some sort, long hair becomes a great insulator during the colder months.
Because your long hair is with you the whole time, you can't do much more than tie it back if the temperature gets hotter.
'Fashion' is not to be confused with aesthetic. The aesthetic purposes of long hair can be pivotal in social context. I've noticed on many occasions that my hair will either drive people away or draw them to me.
Short hair is monotonous and boring in present society. Being even insignificantly different can make a significant difference.
People, most notably females, are curious about my long hair in a place full of short haired men. I can also readily meet new people who aren't pandering around aimlessly like the rest of the lamers in the rat race. These same people aren't averted to the 'extreme' ideologies I uphold. The harmless idiots you can find in public usually believe I am a musician or in some kind of a band.
It can bring more attention to you, but it may be unwanted.
Because people are quick to draw conclusions based on appearance, and many people draw conclusions based on stereotypes, you are likely to be treated as a pot-smoking liberal stoner faggot. The police aren't fond of you either. Workplaces are also less apt to hire you, unless you can convince them you will tie your hair back. (Typically, only cashier and foodservice jobs are avoidant of longhaired males. Why would a hessian want to be a cashier or fry cook?)
I do have long hair, and it's about 4 or 5 inches past my shoulders. I've been growing it for the past 3 years, and I've recognized those advantages and disadvantages, and I can say I've liked it. I'm the only person I know who has long hair. I'm also the only person I know who enjoys death metal and classical literature.
As far as altered hair color, my hair is naturally dark brown, but it is lighter at the ends, possibly from sun exposure. It's nature's proof that you go outside away from the shelter of your home.
tl;dr --- If you think long hair will work for you, get some. If not, then don't. Either way will require some degree of maintenance.