Dwight Sipler , Feb 21, 2012; 07:52 a.m.
User settings are typically stored in flash memory, which doesn't require power to maintain. The clock has a separate battery, which will last for several months. When the main battery is inserted in the camera it charges the clock battery.
If you're planning to store your camera for a year or more, you will likely have to reset the clock, but not the user settings.