I will get to a long answer another time, but for now here is my opinion... 1/4" is plenty thick. 3/16 is too thin even for the cooking chamber. Insulation (firebox) is more important in some climates than others but always helps. RF is easier to manage and does hold temp more evenly across the cooking area. It also uses more fuel because the heat is having to travel twice the distance while also being absorbed by the RF plate. I enjoy using tuning plates (or the lack thereof) to create different cooking zones throughout the smoker in the same way that you create different temp zones on a grill. How often you go through a split depends on a ton of factors, how hot you run your fire, the size of your splits, the efficiency of your cooker, the weather conditions, etc. If you can get 45 minutes to an hour between loading normal 1/4 splits, you are doing OK. Lastly, to quote Warren Zevon, I'll sleep when I'm dead.