I cut my hair at random, based on how long it is. I should honestly get trimmed more often, but I'm too lazy to do it and we cut our hair at home to save money. I do go out like once a year to get it done at a salon too though [my friend takes me to our mutual friend who's a hairdresser, usually on days she's actually closed o.o]
Every month or so? My hair grows super quick and I hate it. I cannot put color in my hair because in about 2 months we'll have to do it all over again and that costs some money.
By the time two months is gone I could have short hair to my hair completely covering my ears and my bangs could reach my mouth.