Do you have an ambient probe to measure your box temp? It might be running high. Temps in an analog #3 can can swing from 30 degrees over or under your set temp, but average out to your set temp. That is normal. Having things done sooner rather than later is actually a big plus. Brisket, butts, ribs, can rest for 4-6 hours easily in a cooler, and just get better. Undercooked and rushed brisket, butts, ribs without a rest on the other hand are awful. Also, remember that meat comes from animals, an agricultural product, and all animals are genetically different, raised differently, eat differently, have different amounts of exercise, and are butchered by different companies at different times in their life cycles, and have different meat qualities. The best anyone can do is allow PLENTY of time for the worst case scenario of cooking time, and give any extra time, if it is done ahead of time, to a nice long nap/rest in the cooler!