I go through about 16 pounds of Outdoor Gourmet charcoal briquettes and a handful of wood chunks during a 12 hour smoke. I shut it all down and it still runs for a while longer, but I always put too much in or refill one more time than is necessary at the end.
I also have some work to do on sealing my door and lid.
To recap, I don't use lump exclusively (like you asked), my door still leaks, and I put too much in to get an accurate measure. How's that for a grain of salt to take my answer with?
18.5" Weber Kettle / 32" Master Forge Charcoal Grill / Modded/Restored NB Bandera