I don't know why any vinyl turning brown is ok, regardless of the "quality". Red vinyl turning pink/white, colors lightening, fading, and prints fading to nothing or chalking, cracking, peeling, whatever is totally understandable, but please explain to me why it's ok for vinyl to look burnt or stained. And of course everyone jumps to "oh, you used cheap stuff eh?"
Of course, I use calendered out here in Florida every day, and very rarely do we get total failures. Most of the time it's prints fading out because of the sun and that happens regardless of the quality of the material.