I haven't cut mine in six years. But it's not as long as I'd like, down only slight past my shoulders. It gets tangled very easily (and nothing an stop it) and no matter how careful I am or what I use there's always breaks when I untangle it.
I used to grow it out for a year or so but lately I've been keeping it short, cutting it every 2 months or so. Most recently, I had it cut a little over a month ago and then last week had the sides cut again, though that was mostly because I also got it dyed (purple and green ).