The saying should be "if you cut your hair it grows healthier". Now that I can get behind. If you are growing your hair out you should absolutely be getting trims every 6-8 weeks. The reason: those pesky split ends! You have to remember that the ends of your hair have been there the longest. More wear and tear. They tend to be dry, frizzy, brittle and broken. The longer you let those split ends hang around the higher up your hair shaft it creeps. So even though you haven't gotten your hair cut in 6 months and you feel like it's getting long chances are you have a couple extra inches of damage that you wouldn't have had otherwise if you would have gotten trims.
Let's do the math....
The average persons hair grows about 1/2 and inch a month. So at 8 weeks your hair is about an inch longer. A trim should be about 1/4 of an inch giving you 3/4 of an inch of healthy lenght. So after 6 month you'd have about 2 1/4 inches of healthy longer hair. Now if you don't get trims your hair would have grown 3 inches but you'd probably have to get about 2 inches cut off because it felt like tinsel. Giving you one measly inch. I made pictures:
I hate when people come in and say they haven't gotten a hair cut in a year and they only want and inch off. Their hair feels absolutely terrible. And when you blow it dry it looks terrible too. I'm not a magician.
Another aspect of this stupid myth.. Yes, if you have short hair you will have to get it cut more. Not because it's growing faster. It just tends to loose shape after a month. 1/4 of an inch can make a neat cut turn into a sloppy one real fast.
