I eventually got build-up from the OneC when I was on VERY strict CG, but most people never do. It also took over a month of daily use for me to notice the build-up. Since you like the OneC, I'd say to keep on using it. If you have to use a sulfate-free shampoo every once in a while, it seems worth it to me.
*Poster formerly known as Bailey422*
Here's all you have to know about men and women: women are crazy, men are stupid. And the main reason women are crazy is that men are stupid. ~ George Carlin