I neglected to mention change frequency. I've never changed mine in the 15+ years I've owned it but I never really used it much and it's been sitting unused for a few years. When I do use it I'm mostly running it through brush on trails in the woods and along my half mile long gravel roadway. I can now mow many areas I originally used it for with my finish cut mowers and just use a handheld brush cutter on the edges.