Also it helps your mat to soak it in water for an hour or so a few times a year. An Olfa Rep told me this at the Road to CA show years back and my mats are in great shape. Like others I do change my blades once I know they are skipping. When I started on the QB people talked about the various sales on blades on the internet and I kept ordering them. Some are rather old now and I need to heat them with a hair dryer to get them apart.