I know if I have to put extra pressure on the rotary cutter to get through two layers of fabric then something isn't right. I change my mat at least every two years. It makes a big difference. The mats get old and dry with use even if they look like new. A blade isn't worth using it skips cuts. A new blade and new mat makes all the difference. I don't understand when some say my mat is years old. Why is it kept that long? It's one of the important tools other then you sewing machine.