Depends on the paste. If using Arctic Silver 5,then yes, you might as well go ahead and change it every year. It has @ 200 heat-cycle effective lifespan. That's not a pc use, that's a cool-very hot usage, so if you run 5 stress tests in 1 night, that's 5 heat cycles, leave the pc idle for days, that's 0 heat cycles. Somewhere around 200,it dries out and is not much better than toothpaste. Any decent paste, like Gelid, Noctua, Phanteks, arctic mx4 etc doesn't have that cycle life and can last longer than the pc itself.