This is interesting - around these parts you are considered a dirty slovenly slob if you don't wash your hair at least once a day. And the ardent gym-goers do theirs every morning (shampoo, shower, blow dry - off to work) then after work hit the gym, run home and shower and shampoo then.....next morning the whole routine all over. And they get this dull crackly horrible looking hair and don't know why. Duh.
I go 3 - 4 days between and in the cold winter months longer - I stretch it out as long as I can. My hair is super-long, lush and healthy precisely because I do not abuse it!
I one time read that if you want long glorious hair, treat it like fine old lace - NOT like denim. it works! Oh - a Fekkai products are absolutely the best. I also go for good ole Tresemme.........l'Oreal products.