This will be about the 6th time I have bought this type of mat from Staples in the last 7 0r 8 year4s. I only weigh about 185 lbs. yet the wheels of my Staples chair make a dent in the plastic. After a year or so the plastic cracks and the shards can be very dangerous especially if working without shoes. If it lasts less than a year I get a free one under warranty but usually it lasts 13-15 months and I need to pay for a new one. Unfortunately there's no alternative.
Appears to be a good quality mat; I have only used it for about a week. Hopefully it will last longer than the last one that was for medium pile carpet that lasted about two years before cracking. In any case this came with a lifetime memory which I guess means who dies first me or Staples.
Bought these as they were reasonably priced. No Staples store close to our location so we could not check them out in a store before buying. The plastic is fairly light weight and dents easily with just the weight of an empty office chair. Used this in a location where the employee only works a few hours a couple times a week and the chair has made dents in this chair mat anyway. The carpet is a very low pile so I think the non-skid tabs on the bottom are actually holding the plastic up off of the carpet enough to help make the dents deeper. Overall I think they are holding up ok but will probably look to a different style/brand with harder plastic in the future.