I have had long hair most of my adult life. Fortunately I have healthy hair so I have donated it in the past and did so again last week. I'm often amazed when I hear about a group of high school students donating their hair since most organizations require atleast 10-12 inches. That's a lot of hair! In the last year I often looked in the mirror and said time for a cut but after getting out the ruler I found I still didn't have the length required.
Last time I donated my hair it went to the American Cancer Society however they no longer accept hair donations. Pantene does not accept hair that is more than 5% gray so that wasn't a resource for me to use. WigsforKids does accept my color hair and requires 12 inches and goes into great detail about how the hair should be prepared for having it cut.