I know you are supposed to run trimmers wide open throttle (wot) but I find much of the time I'm working around delicate plants, close to auto's, rocky ground, etc and rarely do I have the trimmer at full throttle unless I'm in open area's. If the trimmer doesn't last as long then that will just have to be the case. One of the reasons I like the 4 mix is the low end torque. Many small trees and plants have no protector around them and I sure can't see running the trimmer at high rpm's and not nicking the bark. I have only lost one trimmer in the last 10 years. I wore a Stihl 80 completely out after many seasons. So regardless of how they are designed I will keep using them at low rpm in many places.