My main mat is a Fiskars that I have used since 1985. Still in excellent condition. Perhaps the older ones were made of different material? Also have the large Olfa mat. As mentioned by others it is very good with a rotary cutter.
When moving I foolishly left the main mat, 24 inch, in the back seat of my car in hot weather. It was full of ripples. My daughter thought to lay it on the driveway in the hot son. It flattened out perfectly. Hated to think of getting a new mat because some of them smell of chemicals.