My slow cooker has low, high and keep warm settings (no medium). I followed the recipe, up to around 3/3.5 hours in, when I turned it up to high for around 2 hours (and used scissors to cut the sausages into chunks). I then turned it down to low for 2.5/3 hours. It was in the slow cooker for 8 hours total, and came out absolutely delicious.
