Smart miners will keep running their rigs when price falls and others turn off their rigs. When difficulty falls too, they will get more coins from mining in the same period of rig operations, at same cost of electricty. In the long run, when price rallies, miners will come back, difficulty will consequently increase, and they can take profits. In general, they will get higher profits than other miners whom left when price falls deeply. Especially, this strategy should  be applied only for good altcoins, for shitcoins, applying this strategy will end with losses, because shitcoins will end with zero price, zero volume.