To clarify: difficulty adjusts every 2016 blocks. There is no time limit on this. If 2016 blocks were mined in one minute - the difficulty will adjust such that the next 2016 will be mined roughly 10 minutes apart from each other.
but if they then switch off this monster miner again and hashing goes back to previous speed then difficulty will remain to be 20160 times too high, it will then take 201600 minutes to mine a block, this is 140 days per block or 2.3 years for 6 blocks. It will take 773 years until the next difficulty adjustment.