Yep, I've been doing this too, and I'm a former greaseball who used to have to wash every single day. I started out with the no-poo method, scrubbing my scalp with backing soda. That worked for the greasies, but my hair started looking really, really dry (and I didn't want to use any conditioner or product on it). Going back to shampoo, I started stretching the days between washes to two, then three, then four days. I couldn't believe that my scalp actually ceased to produce oil at its former rate!
Then I bought a jar or ASIAM co-wash and started trying that every few days. It worked really well but the directions say you might need to wash with a sulfate free shampoo once a week or so if you have product buildup that needs to be removed. Now I'm using ASIAM co-wash once a week and Johnson's Baby Shampoo once a week (three or four days later). If my hair is stinky or I go swimming I use the co-wash more often. Next on my list is to replace any products I'm using with SLS or silicones with a healthier alternative. So far, my hair has never looked better, or been more manageable!