Do your exaggerations make you feel better ? If your receiver is randomly rebooting, based on your description, it's defective. It is NOT normal behavior. It doesn't prompt you every few minutes when you delay the scheduled reboot either - it waits at least another hour.
I don't think neonturbo is exaggerating, I've been on a second shift schedule since the middle of April; and each night when I'm trying to watch/catch up on my viewing, the Hopper is determined to reboot weather I like it or not. It doesn't do it "randomly" it just keeps asking, over and over and over again, and if you don't say no within 30 seconds, it just goes ahead and does it.
It doesn't matter if I just started playback of a recorded show, or if it's doing Autohop, and it doesn't even care if it's recording (at least an OTA program). I could have just changed the channel, it can even be in pause on a playback; up comes the 'would you like to reboot now' and if I don't see it... reboot. It's annoying, stupid, and make me mad that I miss 10-15 minutes of programming too. I understand their code stinks to the point that it needs rebooted every day, but at least on my 622 I could pick the time, and if I was doing something at the time on the 622, it realized it was in use and let me keep viewing TV.
The hopper doesn't care what you're doing, it just reboots (I know you get the warning, but every 20 minutes, with only 30 seconds to opt out for another 20 minutes is NOT user friendly)