In case you didn't realize: When electrical stuff dies, it is most frequently caused by the same thing. This goes for computers, TV's, welders, anything.
When you bend a piece of metal rod with your hands, you have to bend it one way, then the other, and so on until it breaks. It finally breaks because of metal fatigue, not your super-human strength. When you bend it once, it heats up, then cools down. Continuing to bend it like that eventually creates cracks in the metal and it breaks. The same thing happens inside any electronic or electrical component. The fine wire leads inside an integrated chip, the traces on a circuit board, the windings inside a transformer, all are subject to this phenomena. When you turn on the device, it heats up. When you turn it off, it cools down. It is this cycling that eventually kills the product (vacuum tubes excepted since they have a definite life span). A transistor or transformer can live forever at the same temp.
To summerize: Electrical components like to stay at the same temperature for long life. It doesn't matter if it stays hot all the time or cold. The home stereo that never gets turned off will live longer than the one that does (I know, its not very green to do this). It is this cycling of heating and cooling that companies like Intel put their products through (HAST-Highly Accelerated Stress Test) to predict how long they will live out in the real world.
