It occurs to me that some of you might be interested in an example of the approach one company takes to reliability testing. We patterned our testing to simulate the real world... shipping, storage, the customer.
Shipping means air, rail and trucks. We did drop tests where packaged systems were dropped from a specified height, both flat and on the corners. This to simulate air transport w/ turbulance and hard landings. Then we did vibration with packaged systems strapped to a huge vibe table w/ the acceleration, amplitude and frequency programmed to run. This to simulate shipping in a truck or on a train. Then we did it again with un-packaged systems to simulate a customer riding around w/ the system in his car.
We did thermal cycle testing with systems in an environmental chamber. Temps were stabilized to very hot, then quickly ramped to very cold, then again and again. This to simulate storage in a warehouse or trucking container or even customer taking his system from a cool office and putting in his car trunk in summer, or car trunk in winter to a warm house, etc.
We did elevated temp testing, again in a chamber, where systems continuously ran a test program while at a high ambient temp. The temp was high enough we had strict limits on how long an operator could be in the chamber. This to simulate/accelerate customer power-on hours.
This testing was done on every new product BEFORE we approved it for sale. It was done on hundreds of systems and lasted weeks. Of course, every failure was very carefully analyzed and addressed. As you might imagine, the time this test battery took was a constant point of contention between Engineering and Sales. Fortunately, my old company ALWAYS gave the nod to Engineering. Nothing sold until we said it was ready.
Now I'll admit to some bias, and the process above was for computers, not AVRs. BUT, while I think we were (are) the best, I know other companies do something along these lines. And from our benchmarking and best-of-breed analysis, I also know A/V component companies are included.