Eh, my two hours sleep to twenty-two hours wake system works pretty well in keeping me moderately sane.
Why would a robot need to go offline to defrag their drives? Most proper operating systems have been doing it while running for over a decade. Besides, my robots would use SSDs or whatever technology replaces SSDs in the future. Internal status tests are actually easily performed while the hardware is online. Indeed, it's often better to do so as well, think SMART-capable harddrives.