Hello, all. Recently replaced the first set of grates on a 4-5 year old Q320. The porcelain had cracked off the strips of solid cast iron near the outer ends of the grates, and the cast iron rusted. Being no kind of grill expert, I'd appreciate any help with getting the new grates to last longer. I live in the Detroit Metro area. The grill lives on my covered front porch where it gets used year round, and is stored under the factory cover when not in use. I preheat to 500-550, clean and oil the grill before each use. Any other maintenance or storage tips are greatly appreciated. Many thanks for your help, PW