1. A method of operating an erasable and re-programmable non-volatile memory system, which comprises, in response to receiving a command from outside the memory system having a time budget for its execution: perform any function necessary to execute the command, assert a busy signal outside of the memory system for a time extending beyond that utilized to perform said any necessary function while remaining within the time budget, and perform during the extended busy signal time at least a portion of one housekeeping operation within the memory system that is unnecessary to execute the received command.