There's a lot of 10+ year old CPUs in use, with heatsinks so clogged as to be at their thermal limit all the time, that I think 10 years is a highly conservative estimate which also assumes absolute max Vcore (which if you've seen the datasheets, are far higher than normal values, and something that only extreme --- as in, liquid nitrogen --- overclockers will exceed); it's more likely other things like motherboard capacitors will fail first.