I cut up some old 2"X12" that had been a raised bed and dulled my chain very quickly. I was blaming the resin, but the dirt may have helped. I am thinking of getting a bigger saw to cut some bigger trees.I think the wood you are cutting has more to do with how often you have to sharpen as well as how many times the chain touched the ground. Last summer I cut many green Hedge trees (Osage Orange) and could go all day and resharpen in the morning, then I started cutting Sugar Maples and had to sharpen three times a day. Same Stihl Chainsaw, bar,oil,and chain. I was told the Maples had a lot of dirt in the bark.