Electromigration is a thing, but if you're applying your design rules correctly, it's one you worry about over decades, not months or years. I've had 30 year old ROMs/PROMs fail due to electromigration (presumedly, I didn't decap them and look), but never a CPU.
I used to believe that CPU should be the last culprit. One time for my faulty q6600 system i replaced everything except the CPU and finally realized the CPU was the problem. And it's not even overclocked.
Out of my experience of ~8 PC assembled (super small sample size), 2 CPUs kissed bye right after the 3-yrs warranty period, 1 CPU DOA. the good thing is that good guy Intel replaced DOA CPU very fast.
I assemble PCs for my friends, family and I since 20 years, we have something like 10 servers and 30 desktops (some are more than 8 years old) at work and I never had a CPU die on me.
I guess there are lemons with everything. I'm sitting here still using my Q6600 workstation with no issues. I keep upgrading around it as it's still fast enough.
I am an animator so my requirements are different. A video card makes all the difference for me for viewport rendering speeds. I don't render out that much, but I did notice that my wife's iMac (which is a few years newer than my q6600) renders out at about 2x the speed.
(Electrons are being pushed around by electric fields higher than 1 MV/m, and do smash into things ...)
I'm not complaining about my seven year old machines, but I'm not too sanguine about the current crop lasting as long ...