I second what InaEva said. I only cut it when it really really needs it. If you are gentle and baby it, you only need a tiny
trim every four months or so. I'm talking tiny - just a quarter inch. It also helps if you learn how to trim your own hair. Then you are completely in control of how much comes off.
This has been my favorite self-trimming tool for close to two years www.creaclip.com