I have never lost a CPU to old age, and I am quite old myself. My first PC was a Radio Shack TRS-80, and I have personally owned about 25 computers since. In my company we have had hundreds of computers over the years. None have had CPU failure.
I have had one Pentium MMX processor burn up when the fan (bushing, not ball bearing) on the HSF failed. How long it ran without the fan I don't know, but I contribute the CPU failure to failure of the fan.
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