I have had my Char Griller coming up on 5 years and I still absolutely love it. Do not like cooking with gas so my setup is the charcoal and side fire box, which is used for both grilling and smoking.
Treat the grates like you would a cast iron pan. Gently rub off the pieces stuck to the metal and do not go to town with a steel wire brush. The seasoning will be rubbed off and you will need to recoat and bake. I simply keep a pressurized spray container of olive oil used for frying and lightly coat the racks before cooking. Not only does the metal season itself when this is done, but the food is less prone to stick. Doing this the grates still look new and have zero rust.
Storage wise, mine has been under cover everyday it has not been used. Not in the garage, just the standard grill cover. This year though I did take the wood off and sand/paint/urethane it and made it look brand new again.
I highly recommend this grill to everyone who is a home outdoor grill master.