I'm wondering how many "Blade Sharpenings" you can get out of a set of Fusion Blades before they are no good? I'm averaging about 2 sharpenings. Also what is the best way to sharpen Fusion Blades? w/ a electric BENCH GRINDER or by hand with a FILE tool? I've heard some people say that a bench grinder heats up the steel too much and will make the blade go dull faster?? Others swear by HAND FILING a lawnmower blade. Whats the best HAND FILING tool out there? I've seen some lawnmower blade "sharpening machines" that cost big money....... I wonder if they are better than a plain old Electric bench grinder?? does anyone have one or tried one?