Good luck with that. My experiences certainly don't match yours. I've always been an overclocker (even from my first 8086, using a clock crystal!) and I've always been able to tell you exactly where the thermal ceiling is on anything I'm overclocking, because that's always the limitation for me.
Like right now. My QX9750 wasn't that hard to get stable at 4.2 GHz, I have screen shots showing the results. Unfortunately it was impossible for me to keep it under 72C at that speed, and >72C you start a timer on this CPU. In the next 90 minutes or so, it's going to fall on its head reliable as can be. At 72C it will run 100% load all day long (yay BOINC). At 73C you've got somewhere between 0 and 90 minutes.
I've found that heat threshold on everything I've ever overclocked. GPUs and CPUs alike. Never in my entire life have I found a CPU that would run 100% load so far beyond its rated thermal cap for any length of time. You must have incredible luck picking CPUs, or you're running a bunch of laptops haha. Think all the mcpus are rated for 100C abuse.