I used to wash my hair daily. Then I decided I didn't have the time, went to washing twice a week. Now it only needs washing twice a week - going to start eking it out further soon! Took about 3-4 months to adjust to this schedule.

FWIW, soap helps get you clean, but scrubbing with water will do just as much good. You don't need lots of product - if any at all. My skin has never been better since I stopped using products on my face (well, eye make-up remover and moisturiser, but no soap or cleanser). Either that or I'm a cheapskate who uses very little shampoo, conditioner and bodywash! And only free bottles of eye makeup remover - although that comes with the pricey moisturiser.