I have used one of my slotted rulers for about 8 years. The only time I ever have problems is when I get into "automatic" zone and forget to but the blade in correctly. I have since bought several more -- I really love them. I have not cut the mats up, but have had a couple of blades go south when I hit an edge..
I use either the 45 of 60mm Olfa cutter -- I have had issues with the smaller one in these mats, but then I normally cut 4+ layers.