In today's versions of Windows, you need to restart your PC for fewer activities. If you installed some driver, made some system-wide setting change, installed updates or if you uninstalled a program, Windows may need to restart. Except for these tasks, you can mostly avoid doing a full shutdown or restart and simply hibernate or sleep. Windows 8's hybrid shutdown in fact logs you out and hibernates. So if you ever need to find out how long exactly how PC is on since the last reboot or full shutdown, you can find it out easily.