I am already on my second mat, and it is much better than the first one. the first one i replaced when i would try to cut, and it would cut jagged because of all the cuts and no longer smooth. i found when it became too difficult to cut it was time to replace. i am using a Fiskars now self healing mat now and have not had any problems yet. the only time i would think of replacing it is if it got to the point of being too rough to work with. i am thinking of getting a second one, that is a bit larger in size, only because of now setting up a work area just for modeling. if i do, it will be another Fiskars.