Say that consciousness has a use, a functional value it provides for the mind, then there would be phases where its work would be taken over by automatic processes that no longer required its contribution, and isn't this just what is see in many everyday activities, but also in particular in so called 'flow states' in which self-consciousness is 'off-line'. You could speculate the the ultimate flow state would be so frictionless as to be entirely unconscious - except for a background of a diffuse contentment. This might better approximate the inner state of a p-zombie, who might understand what is meant by consciousness as regard it as the sign of an inferior kind of functioning. So much for consciousness as a theatre of qualia, including thought-qualia, but the other function of consciousness, providing an irreducible distinction, a singular and independent point of application remains untouched.