Last June (2012) I purchased a TiVo Premiere with lifetime service and about 2 weeks later I (not 100% sure why but I did) upgraded it with a 2TB drive.
The original activation date according to Tivo's web site was November 15, 2010 so the original owner had the unit for just under 2 years.
I just plugged the original 320GB drive into my home Linux system to get some stats on the original drive and what I found was interesting.
Total power on hours was 4030 hours or ~168 days (8760 hours in a year), the drive had 70 power cycle events, and 1 Raw Read Error, everything else was unremarkable.
Now about 14 days worth of those hours were mine plus several power cycle events (turned it on when I received it and probably a few when I duplicated the drive).
Well now I know why the previous owner sold the unit he obviously didn't use the unit much. I guess I'll never know what he reasoning was as to why he purchased it and why he stopped using it. Its obvious why he sold it.