I have several Olfa mats in varying sizes and have had really good luck with them. Two of the larger ones are over 10 years old and used a lot. I do try to move around where I cut on them so as to not be cutting over and over again in the same spot. I bought a Fiskar brand one that was part of a set of ruler, cutter and mat. I kept it stored in the cardboard package it came in and it warped the first summer I had it. Yes I know it gets hot in Florida but not that hot! It wasn't in the sun at all, stored flat and I didn't treat it any differently than my Olfa mats and never had a problem with them.