Way back I experimented with the not washing your hair at all method. After two weeks it was really itchy and lank and I nearly gave in. However, by the end of week three it had settled down.
It used to get wet in the shower, and obviously I brushed it every day. What I didn't do was allow any chemicals near it. If I went swimming in the sea or pool, I'd rinse it very thoroughly.
I stopped when I decided I wanted to dye it, but for six months I had zero shampoo/conditioner bills.