I've heard of the no shampoo theory and have read about several people who have put it to the test. Allegedly if you can keep it going, for, I believe a few months, the hair is supposed to feel wonderful cleansed of all chemicals, and hard to believe, apparently no longer feels dirty. Don't know if any of those who followed such a regime carried on with their non washing for the foreseeable future. After a couple of days I feel a great need to wash my hair so can't imagine I could ever follow such a regime and in any case I colour mine as well so it would still have to be shampooed at such a stage. However, I guess if one were to step back in history there would have been very little hair washing going on.
Good luck with it OP.