I've had my two olfa mats for about 20 years; only problem I had was with the one I lent to my daughter (need I say more?). I have always stored them on edge (behind a bookcase, desk, couch, something that will help it stand straight). I love them but realize I may need to replace them soon. The one my daughter borrowed got a bow in it (she stored it next to her frig) so I cut that end off and now it sits perfectly on my sewing table.