Originally Posted by El Ropo
Don't open it for anything till you hear the sizzling start to calm down. You can place your ear close to pit or exhaust and hear the sound the meat is making. No need to peek. When that sound starts to get a bit quieter, they are probably about done, but I'd check at 3.75 hours anyways for spares depending on how meaty they are.
That's one drawback to an insulated cabinet smoker like a Backwoods or FEC-100. You can't hear the sizzling. :D