It has been verified quite a bit on the effects of low temperatures coupled with large delta T's on package reliability performance. Take a look at the JEDEC 22 and Milspec 883 standards. Normal Temperature cycle B is an accelerated stress test than can go as low as -55C to 125C and is used to evaluate a usage condition delta T of 40C from Room Temp (Intel's website has some interesting papers on package reliability performance). Below -25C temperatures coupled with 50C cycling shifts have been experimentally verified to have a negative impact on product life. I would completely agree that most OC's don't care about this as whats the differance between 10yr rated reliability performance vs 3yr or 2yr (it will be old tech by then). Whether we care or not it does occur and my point was to minimize the number of times it is cycled to room temp from such a low operating condition (meaining -40 or less) in order not to place yourself it that risk catergory.
As for the heaters, you have a valid point about the shock affect not cause instantaneous problems. Once again though, its the temperature gradient and time to temp that affect the reliability performance. The heater would be used to control the gradient via a PID that could power down once a certain POST code is reached.
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