This is the second matt that I have purchased. I use it on a plush carpet and over time it breaks up. It does seem to discolor over time. I can't remember how long I have had the one I have now. It does make it possible to roll my chair on the carpet and saves the carpet from the chair.
I bought one 12 years ago that was of the same thickness. It started cracking about 2 years ago. finally had to replace it. I spend about 4 hrs. in the computer room a day. My advice is use some leather gloves to handle it. the studs are unforgiving.