Keeps 4 days refrigerated and freezes 3 months — one of the best batch-cooking dishes there is. Freeze it in the juices rather than dry, and reheat gently with a splash of liquid. It reheats better than almost any other meat.
It's undercooked, not overcooked. Pork shoulder needs about 195–205°F internally for the collagen to break down — well past 'done'. If it resists the fork, give it another hour.
It adds flavour but isn't essential in a slow cooker, where the surface never crisps anyway. In the oven method it's more worthwhile.
Raw pork shoulder loses about 40% of its weight. 3 lb raw yields roughly 1.75 lb cooked — eight generous sandwiches.