Last dramatic change was on the very last day of school 6th grade year, I got over 6 inches cut off...and I did it that day on purpose because I knew my friends would all hate me for it because they were in love with my long hair.
That way, I didn't have to hear about it over the summer.
My hairdresser (who I don't think I'm going to use anymore if I can help it) always bitches that I don't come in to get my hair cut often enough...I let my roots grow till they're several inches long, and only get my hair cut 2-3 times a year. It's frickin crazy expensive, so she can just shhhh.