Expansion actually infers finite and infinite for any consciousness to expand, it also needs limitations, boundaries.
Is therefore motionlessness (timelessness) this un-conscious?
I think this un-consciousness doesn't exist for it's not of any kind of energy, it can only exist within a consciousness which makes it a creation of consciousness to start with. So yes you are right, this ever expandable (infinite) consciousness has it's limitations.
The yin can't exist without the yang, does this mean consciousness can't exist without the un-conscious as well? The yin can't exist without the yang for without the yin the yang has nothing to compare it's existence with. Consciously speaking, the un-conscious has to exist to prove that consciousnesses also exists!! A paradox as always but quite comprehensible.