How long do you wait until your next perm?

if you are african american DON'T PERM YOUR HAIR it thins out your hair trust me my sister got one and a couple years later her hair was falling out and it was really thin and its just not a good idea.... i think you should just leave your hair like it is so it can grow healthy because my hair is half way down my back and i've never put a single chemical on it just olive oil(lots) lots of conditioner and things that give nutrients to your hair and sometimes my mom parts my hair into little sections and puts oil on my scalp so it doesnt dry out