Many find the showerless yom tov to be quite a trial. Consider what it would be like to not shampoo for more than a month?
Amber Genuske couldn't help it; when in Kosovo, the bathing conditions were quite primitive and not hair-friendly. But when she arrived home and blissfully bathed, she was amazed how healthy her hair was.
She now only washes her hair one or two times a week. Funnily enough, so do I. When my hair gets a little oily, I prefer cornstarch to dry shampoo (the fragrance gives me a headache and makes me sneeze); I just sprinkle a little in and it absorbs any greasiness.