No desktop CPU I’ve ever used has remained stable at 100 degrees.
My 14900k crashes almost immediately at that temp.
3 hours at 100 degrees is obscene.
Besides AMD CPUs of the early 2000s going up in smokes without working cooling, they all throttle before they become temporarily or permanently unstable. Otherwise they are bad.
I've never had a desktop part fail due to max temperatures, but I don't think I've owned one that advertises nor allows itself to reach or remain at 100c or higher.
If someone sells a CPU that's specified to work at 100 or 110 degrees and it doesn't then it's either defective or fraudulent, no excuses.
Max Operating Temperature: 105 °C
14900k: https://www.intel.com/content/www/us/en/products/sku/236773/...
Max Operating Temperature: 100 °C
Different CPUs, different specs.
And any CPU from the last decade will just throttle down if it gets too hot. That's how the entire "Turbo" thing works: go as fast as we can until it gets too hot, after which it throttles down.