Wiping them off with baby wipes works wonderfully. Also, when wiping them off no longer works, I use painter's tape to tape over my edges (outside of cutting area) and use a repositionable glue stick to re-sticky the area. Repositionable spray also works but I appreciate the extra control the glue stick gives me. The actual mats can last a long time giving you more money to spend on fabric
I have had a cricut for over 5 years and never had any problems with re-stickying my mats.