A pork shoulder is only going to take smoke for about the first 4 hours or so. Lots of people after that will foil (I foil at 165deg instead of a time), move it to an oven for ease of cook or both. I took cook to 203deg and then rest a minimum of 1 hour. Often I wrap in a bath towel and place in an insulated cooler for a few hours or so until it's time to eat. Lowering the stove to 100deg or so accomplishes a similar result.