There’s a movement that was/still is (?) call “no ‘poo” (or something like that) that says you can go quite a long time time, like weeks and weeks and weeks between hair washes.
What happens is (according to the no ‘pooers) is: you wash your hair, it strips away all the natural oils. Your body reacts by producing an over-abundance of oils to compensate, you look in the mirror a day or two later and say, “OMG, my hair is so greasy!” and you wash your hair, it strips away all the natural oils, and the cycle continues. It takes about six weeks of not washing your hair for your body to get the balance right and after that, it sort of works out.
I do think there’s something to that, as I had to go a few months without washing my hair while being treated for rosacea, and that’s pretty much what happened, and I had shoulder-length hair at the time. The first few weeks were pretty hard to deal with, it was really nasty, but then it worked out. I wash my hair once a month now.
MrsT…I’ve posted pics of her hair before, incredibly thick and kinky, and she washes hers every six weeks or so. Both our hair stylists are also of the opinion that people generally wash their hair far too often.