Your computer SHOULD be able to handle 100% usage full time.
But as we all know there are some "inefficient" cooling being used in computers ( especially laptops )
There are many rigs out there that reach critical temps if they stay @100% load.
Although your computer should be able to do it , many stock solutions fail to do that ( especially during summer )
Remember that you should be fine until 95º
; ( this number varies from computer to computer ) , and ops numbers show it's near the threshold but not passing it so it's stable. ( your computer will probably reboot or slow down if faced with extreme temps ).
What I can state is that running in 100% load does decrease your cpu lifetime cycle assuming it will cause greater temperatures.
In the end , higher temps = lower lifetime , but the difference is not that big.
I still have my oced P4 working :P and the lifetime of a cpu is rather large.
I'v also heat about the rule "halving of life for every 10 °C" that is applied to insulation systems , I think it's known as the Arrhenius equation. But I doubt it's that simple.
No one can tell you if you how much does extra temps take from your cpu lifetime , or if it's even noticeable , and with cpus that last long , it may end up not being a problem ( unless you burn it due to temps )