I've got a GREAT question
Sorry, I meant GRATE...
Those words are curiously interchangable on this website......like nowhere else, apparently.....
I have regular ones that have lasted 11 years, still going, not with quite as much use as you're talking..... more kettles/greats in a wider, hence slower, rotation......most everything stays pretty well coated in smoke & bacon grease at all times........
As we were talking about down at the meetup on Napa.......scrape the coating off & there's clean bare porcelain underneath a lot of the time.....that's the kettle inside......the grates, taking more heat & being coated differently will give up the ghost, but keeping a seasoning & avoiding screaming high heat mostly has worked well for me......
If you do have rust, one possibility is to scrape it down & soak with vinegar & baking soda sprinkled on.......soak like that, then scrape again & clear it & season with cooking on it & spreading the resulting oils around or spray on cooking oil as a seasoning / preservative.......
The stainless I have not used yet.............