Bought a Honda Brushcutter. Came with 10" 80T blade. Used 4 hours and dull. The blade says "don't sharpen". Any reason these can't be sharpened? Is HONDA just wanting to promote buying new? I can't afford a $20 blade every 4 hours. What about carbide tipped blades? Can they be resharpened? The Honda supplied blade worked excellent for the brush I was clearing and the 2"-3" saplings I used it for instead of a chainsaw. Any blade recommendations that last longer or more cost effective? I tried one of those $10 four blade cutters, but it's pretty worthless for what I'm doing.