Well, I don't do that for a living much, but, I can say, after 12 hrs, we tossed the spark arrestor/ muffler and disabled the brake, even on brand new saws. 2 kinds were all we used, Stihl and Husqvarna. The Husqvarna has (or did have) and aluminum head. Gotta let her get cool after about 10 minutes....
