You could save a lot of money by never going to a barber and a lot of money by never speaking with a lawyer. Of course, you'll look like a fool in both instances.
Washing your hair every day puts more wear and tear on it, and it's time consuming. If you have short hair, you get away with this because you keep cutting your hair long before it gets worn out. So only once or twice a week will I actually wash my hair (and use conditioner, this actually becomes important with long hair). Most days, I tie it up into a bun before showering so it doesn't get wet. You might be able to find another solution. Depending on your water quality, your hair might smell gross if you just get it wet without washing or at least conditioning it.
After showering, I generally brush my hair, especially after washing it or if I want my hair down. If I'm in a hurry or it doesn't look good loose, I just tie it back in a ponytail. There is literally nothing else you have to do to make it look presentable. After a certain length it doesn't really get in your face unless it's especially windy or something. If you want it loose during some sort of physical activity, I've noticed a lot of longhaired footballers will wear a thin black hairband around the base of the skull and the hairline--if you do an image search for Leo Messi or Didier Drogba I'm sure you'll see what I mean.
Human hair actually stops growing at a certain point, or to be more precise it grows at the same rate that it gradually falls out over time leaving you with a consistent terminal length. Mine seems to be around the small of my back.
As you grow it out between an ordinary short hairstyle and shoulder length, you're likely to look kind of strange for awhile, and have no good way of managing your hair. On male longhair web forums, this period is usually referred to as "the awkward phase". You might be tempted to get haircuts so you can at least have a decent medium length style at this point, but really that only makes the awkward phase take longer. From a short hairstyle to shoulder length usually takes within 2 years, but only the middle part of that is likely to be too awkward. From short to shaggy it just kind of looks shaggy, and from almost-shoulder-length to shoulder length it just looks increasingly awesome, but there's a bit of an awkward gap between "nice and shaggy" and "almost shoulder length" where you can't tie it back, you can't quite keep it all tucked behind your ears, and it gets in your face.
One last point--I suspect my hair is naturally very attractive, so I'm certainly not going to guarantee that women will approach you on the street and say they're jealous of your hair if you grow it out. Generally, most styling and hair care above and beyond not cutting it, washing it, conditioning it, and brushing it does more harm than good in the long run. The whole point about barbers saying everyone needs a haircut rings very literally true--hairstylists and hairdressers will suggest a variety of treatments, products, chemicals, cuts, and other solutions to often completely imaginary, self-solving problems like split ends, based upon completely fictional notions about the physiology of hair.
And that is certainly more than I ever thought I'd have to say about hair on Hacker News.
self-solving problems like split ends
Could you explain that? I though split ends forced to cut one's long hair regularly.