I have a sneaking suspicion that its not so much time is running out but whatever the sound was, may be stirring without zodiark's influence to keep it in check

The other thing that's been bugging me: why haven't we seen any evidence of the ascians trying to fix the void? If they want Zodiark to get to his full strentgh they need to rejoin the worlds...but the void is stated to be completely useless to their plans, much like how emet selch said there was to be a similar event on the source to break the barrier for the 8th or it would be useless

The void was their first attempt at rejoining, so they have had ample time to undo it