If you want to sharpen your blades I recommend the Tru Cut electric blade sharpener.
http://www.graceframe.com/site/rotarycutting/truesharp You want to buy direct from them as there are knock offs that don't work. You also want the top of the line model. We have really extended the life of our blades using it and rarely have to buy new ones. I take the time to sharpen the blades whenever I have the least bit of trouble cutting. If you let the blades get too dull or get a nick out of them then you will have trouble getting them sharp again.
PS I also love their rulers and rotary cutters.