I've been looking at BGE for years and they never seemed to be very convenient when it came time to add additional wood or charcoal. So if you're going to smoke something for 8 to 10 hours how do you go about keeping the fire going? And another thing I was wondering about. When you're smoking for long periods, you need to protect the meat from the direct heat source so how do you go about doing that. I know people do all these things, I've just never seen it done and it seems I'm missing out on a great piece of BBQ equipment.
I don't own one but have been reading Kamado cooker forums for years (BGE, Grill Dome, Primo, Komodo Kamado, etc.) and am still considering buying a Kamado-style cooker. (Dream cooker is a Komodo Kamado but it's pricey!) Almost all owners have had no problem doing an 8 to 10 hour cook. In fact, most owners say that they can do two 8 to 10 hour cooks on a full load of charcoal. So while it's inconvenient to add charcoal (you would have to remove the food, grill, etc.) during a cook, you won't need to as long as you put enough in the beginning.
Most people use a Plate Setter - it's a piece of equipment placed over the charcoal and heat source; some other makers have a lowered grate (to either use for grilling at a lower level and higher heat) that you can also put a small pizza stone on to deflect the direct heat (I believe Grill Dome offers something like this).
Check out the forums for these cookers. There's THOUSANDS (literally) of threads and users out there who write about these kinds of issues and their experiences.