The running theory was that washing it more than weekly would ruin it. My Mom's theory was that washing it more than once a week was a waste of shampoo. Waste not, want not. Either way, once a week was the rule.
The movie South Pacific came out when I was about 10ish and I was besotted (love that word) by it. My Mom had seen it on Broadway with Peter Pan (Mary Martin) and had told me that for the run of the show, Mary Martin washed her hair every single night while she was on stage.
I was just amazed by this. I had seen Mary Martin and I knew her hair wasn't ruined. I was so confused.
Tonight I watched a PBS special about Oscar Hammerstein and they showed a clip of Mary Martin from South Pacific and all I could think of was how clean her hair looked.
My brain is just for fun these days.