I have to figure there have been at least 1 million dead 360's over the life of the console. They should have plenty for this sort of testing. You figure 4 years ago the sales figure was 10 million and a 10% failure rate being standard. The actual failure rate of the 360 was abysmally higher and only so many of them were refurbished. KILL EM ALL!
Edit - Scratch that the 2012 sales figure is 70 million. Dear god there has to be alot of dead 360's out there!