To get the most out of your router bits, take them to a professional sharpener. They will be able to keep the bit's correct cut and shape while restoring it to like-new sharpness.
However, if you can't take the bit to a sharpener, you can accomplish the same result by using diamond hone on the two edges of the cutting blade. Apply water to the diamond hone and lay the flat side of the bit against it. Stroke the bit back and forth across the hone, removing thin layers of metal from each pass until.