ServSafe says" 140°-70° in 2hrs 70°-45° in 2 hrs. It's not 6 hours, its 4 hours total or the bacteria starts to produce toxins into the meat. I pull the bones and pull them in half to cool faster. Briskets I cut the flat away to make it thinner to cool faster. If you use a good cooler and pack with towels to take up any space left in the cooler, you will not have to put back on the heat after only 2 hrs.