My computer desk chair with 5 wide rollers started to sink into the mat with only a few days of use. I can see this failing in a mater of months. The mat material used is not suited to this type of use. By the way I am not overweight.
I've had this chair mat a few weeks and so far it is great. I can't speak to the longevity of it but it seems to be strong and well-made it provides good support for my chair over fairly thick shaggy carpet and it doesn't smell like petroleum. I hope it lasts a long time without cracking like my last one did.