The xbox doesn't fail because the board bends lol .

Its fails because the CPU in the board isn't soldered correctly to the xbox 360 and this cause the solder to fracture were it connects to the PCB. You can use several methods to fix the problem and all the methods involve heating up the PCB / CPU inside the xbox 360 to cause the solder to re flow and this fixes the problem.

The reason for the problem is the factory were they were made is on a budget by Microsoft and they have to make these as cheap as possible so that they keep the contract with Microsoft. Due to this fact they use sub standard procedure to make the hardware and this in turn is were the hardware fails.

Its all down to economics and the life span of the console. Console are not made to last beyond 3 years.