I am now on my fourth DVR in 20months. All have been Scientific Atlanta units (two SA-8000 and two SA-8300 units. All were furnished by Cox. The first died within amonth, the second lasted 8 months, the third about the same. Is this usual behavior for these units?
Not for me. My SA8300HD is still working perfectly for about a year and a half.
Disk failures are common. I have had over 10 DVR's from various manufacturers and it is not unusual for them to fail in a year. Many of them just run very hot.
That's one of the nice things about renting :)
It all depends on how hot the hard drive runs, if the box you have does not have a fan, you might consider adding an external one. (or if your renting and need a new one, a towel could help it's demise...)
I had a couple of Motorola DVRs go bad. Then I found a page about them getting to hot. I took the glass door off my tv stand. It was building up a lot of heat. That keep it cooler and running longer.