I Co-wash every other day so using shampoo is only on an 'absolute must' basis ( i.e, product buildup, 3 days before henna treatment, if I decide to flat iron, etc.) But I dont wash my hair so much as I wash my scalp.
ETA: I shampoo my scalp and just let it run down the lengths of my hair. Once upon a time I used to pile my hair on top of my head, plop a big chunk of shampoo on and just go to town rigerously... big no-no!