I have had trouble nicking my blades too, so I bought a sharpener from Hancocks or someplace. It seems to work pretty well.
But what I have learned from the books and magazines I read, you should change to a new blade every time you start a new quilt. And they also suggest that you only cut 4 layers of fabric at most each time. This will keep you from having wobbly cuts at the fold.
One day someone will invent a titanium blade that never dulls or chips, but until then...