I got almost 7 hours burn time in the WSM today with just 1 Weber chimney + 10 briqs, using the Stubbs charcoal. I cooked 3 racks of Costco Pork Loin Back ribs, rolled on the top grate, using Apple for smoke. Fired up the way I usually do, with the torch, vents wide open, hit 220* and added the ribs and tuned down the vents and it stayed steady 235* dome for 3 hours. Flipped the ribs and sprayed with Apple juice and opened the vents and raised the temps to 250-270* to finish up (BRITU like cook) Ribs were done in 5.5 hours, guests were late so they got foiled an into the Cookshack to hold.
Beautiful smoke ring-so much that one of the guests politely asked my wife if she could microwave them, because she thought they may be undercooked(pregnant mod!) My wife explained that they had been cooking since 6AM and that it was the smoke ring and not raw meat. No pics so it didn't happen, but I couldn't make this up!
Conclusion: I'd use the Stubbs again for low n' slow- no off smell whatsoever and about the same amount of ash I'd get using Rancher (8 bags left) I'd like to do a long cook and grill with it to get a rounded opinion.
If you see any give it a try!