80 or 100 percent menas that you are using it that much, not that is dying
have you ever reinstalled windows on it, run a antivirus or a malware scan?
use malwarebytes or plan a reinstal, if you change to a new cpu but keep a windows installation full of crap, virus, the new cpu will do the same as the old one
a cpu used to 100% means that is doing alot, not that is dying, a cpu that will fail will not support 100% load, it will just shut down and never turn on again