Jon SS,
Computer hard disk drives actually last longer if you keep them on all the time rather than power cycling them. That's a well known computer industry fact. Heat expansion and motor wear from warmup-cooldown spinup-spindown is worse than keeping the hard disk running 24 hours a day. The heads are parked anyway.
I don't know if the 8000 PVR puts the hard disk in sleep mode but if the power consumption is the same, then the hard disk is still spinning even in the OFF state. (maybe you can try listening to the 8000 PVR, to see if the hard disk is still spinning) (try unplugging an 8000 PVR while it's "off" -- if you hear a hard disk spindown, then the hard disk was spinning while the 8000 PVR was in its so-called "OFF" mode)