Gaara's move was the "Forced Sleep Technique" and it's an INCARNATE of sand that's BOUND to him. The demon isn't dead, just repressed for now. Gaara's stuck with it for life (unless a cure does indeed exist) and will have his mental constitution eaten away at every time he sleeps. But he probably doesn't ever. Why would one need to force themself asleep if they haven't slept in weeks? He's probably immune to sleep by now.