You know about seasoning a cast iron skillet. Some people rarely clean their smokers other than a grim build up. Some places the griddle has decades of flavor in it and their burgers are world famous because and only because of that griddle. Well I've been doing the same to my trusty weber charcoal grill for at least two years. No cleaning and there is a nice build up of burnt stuff on the actual grill surface (grate), at least 3-4 mm. I am really starting to notice that the flavor of the crust on everything I cook has an unbelievable flavor to it. Made some burgers last night and the browning and grill marks on the outside were out of this world good. I don't think I'll ever clean my grill unless it gets unusable. I remember going to a cook out at a pretty good chef's house years ago and when he opened his grill it was coated in blackness. I thought he was crazy/lazy and just asked "guess you haven't gotten around to scrubbing it down, eh" His answer - "don't ever clean your grill". It didn't make any sense at the time and thought he was crazy, but I'm a believer now.