I have been sharpening my X-acto blades for about 30 years. I use wet/dry sandpaper used to sand down car paint, I believe it is 320 grid, placed on a flat surface. I give it a few strokes every now and then. The blades may be lasting me 10 years, but I don't really know. I am always afraid someone will be cut with the discarded blade. By sharpening the blades I have less things to worry about. I see no need to critisize what ever method you use. Do as you like, but be aware of other methods.