You can see a big difference in old kettles vs newer ones. 60's, 70's, and 80's grill have a much glassier porcelain. I don't buy into normal cooks causing problems with grills. The grills are baked at somewhere between 1300-1500 degrees (off the top of my head), so your average cook is not going to be anywhere close to that. I think rust and cracking is mostly due to manufacturing defects. Most of the time it happens at weld points, like where the grate straps, handles, and leg sockets are welded to the bowl. If there is anything wrong with those places the expanding and contracting due to heating and cooling is going to magnify any flaws. Just my two cents.