No, I do not wash w/ shampoo. I use human hair, so when I feel my hair is dirty, I run cold water through my scalp and massage, because I use little to no product while in the sew in I dont have much build up.
I did the shampoo thing, before, but felt like that did more harm then good, because i always think i wash it all out, but dont and it turned out to dry my hair and of course some matting was going on
ETA. A sewn on me will last between 1-3 months, depending on the hair and the way MY own hair is braided and most importantly the status of my hair