I use TruCut's $65 electric sharpener. It works great. I sharpen blades at the first sign they are getting dull. It greatly extends the life of the blades. I also love, love love their 24" ruler and companion rotary cutter. I tend to wobble the blade or have the ruler slip when cutting WOF. No problems with these. I have also attached their grippers to the bottom of the rulers.
http://www.graceframe.com/site/rotarycutting/truesharp. I would recommend buying from their site to be certain you are getting their sharpener and not some knock off.