As long as a CPU's temperature stays below the manufacture-specified maximum, does a CPU's average temperature affect its lifespan?

For example, my laptop's maximum CPU temperature as specified by Intel is 100(C). If I run it at 90(C) for a period of time vs. running it at 40(C) for the same period of time, will there be a difference in how much of the processor's life that has been used up?

Is there credible scientific research on this subject?

My reason for asking this is that I am trying to determine whether to increase my default fan speeds in order to lower the temperature that my CPU idles and works under light load such as typing this question.

P.S: even though I've tagged this 'overclocking', this question is not concerned with the effects of overvolting a CPU.

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    Most likely, but even then, something else would die before the CPU. Look at old computers, they're still working fine even after 20 years, and the ones that don't work usually have a faulty motherboard or PSU. Personally I've never had a CPU die on me unless it was physically damaged or totally burned. – user256743 Mar 5 '15 at 17:48
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    A CPU is designed to run at its maximum speed and provided it stays within its thermal limits doing so will not affect its projected lifespan. Of course this question seem extremely broad honestly. – Ramhound Mar 5 '15 at 17:50
  • @AndréDaniel I'm just curious. I know most likely that my computer will outlast its useful life given my habit of always using the latest and greatest software. I just want to know if a higher temperature results in a higher rate at which the electronics inside of it degrade. – danielcg Mar 5 '15 at 17:54
  • @DavidPostill No, because I am not asking about the CPU load, just the heat. – danielcg Mar 5 '15 at 17:57
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    @danielcg actually I believe what kills electronics isn't heat (well, unless it melts) but it's the heating up/cooling down cycle that make matter expand/contract and induces stress on it, and it eventually breaks. Thus, it would be best to run the CPU at a fixed temperature no matter the load (just like car engines do). – user256743 Mar 5 '15 at 17:59