Cutting mats can wear out over time, especially if you are going over the same surface multiple times. To make the most out of your mat, always use a sharp knife when cutting, and don’t expose it to very hot or cold weather, which could cause the tiny pieces to unstick.  Even with the best care, cutting mats will wear out, and you’ll eventually need to replace them. You can tell if your mat is on its last legs by looking for any holes or tears in the product where the pieces themselves didn’t fuse back together. At that point, you may need to replace it.