Yes, that's right.
Define prolonged time. 24 hours, 24 days, until degraded and then sell it?
72°C is listed on Intel's site as Tcase, the CPU case, add 5°C for Tjunction which is CPU cores, this is what CPU temp monitoring programs use. So when using SpeedFan, RealTemp, CoreTemp, etc. max temp is 77.7°C.
If you search around enough you will find many different "operating temps" listed.
You will find that many people especially on OC sites will say anything under TJmax is OK, if they are pushed they will say it's ok because they plan on selling the CPU in less than a year (to some poor unsuspecting person) or they don't mind tossing it in the garbage and buying a new one for the sake of getting the bragging rights to high long term speeds.
Knowledgable members at good sites always give the disclaimer: OC at your own risk.
Running CPUs at high temps has its risks, each CPU runs differently, speeds obtainable, temps, etc.
Heat kills electronics.
The manufactoring processor grading is known as binning, when the processors are made they are tested and separated by the results of the tests and then put into bins, these are used for different models, i7-980 to the lowest models. Some i7-980s run hotter than others due to the quality of the transistors and won't OC without more heat compared to another with the better transistors.
It's the luck of the draw.
Each person has to decide for themselves if they want to OC, and decide the level of risk/level of OC.
Heat is the key to the risk level.
I OC'ed until I found my heat wall, with my cooling system, then backed it down so I could run at a safe temp. But that's just me, some people must reach that 4+ GHz level no matter the risk.
Decide your risk level, start slow and find your 'Walls' and do what you can to keep reasonable temps.
Unless you don't mind tossing your CPU and getting a new one, then go ahead and crank it up.