Well in my experience, a hard reset is the powering down of the device by removing its power, as opposed to a soft reset usually triggered by pressing the reset button within the devices software. A hard reset doesn't give the device time to do some of the things it would normally do during a soft reset, which isn't always a good thing, but can sometimes fix certain issues.

To better answer the question, no I don't believe that it will reset to factory if you remove it from power for that long. The type of storage it uses should be non-volatile which means it can retain data without being powered (similar to a memory stick, and the opposite of RAM).