I also have the hard black plastic one bought many years ago from IAP and it does look good except after a few years it developed a small sag. I had to go back and trim the glove box door to get it to close. Sag does not appear to have gotten any worse since then.
I've had mine installed for about 4 years, now.
No warps, sags, bends, discoloration, and no change in appearance from when I first installed it.
My car sits in my attached, but unheated, garage and regularly sees seasonal temperature swings of about 30 degrees F to 110 degrees F.