You ever notice how meat just laughs at your timeline? Jamie101 is totally right about adding an extra hour. I tried a new short rib recipe last weekend that said 3 hours, and they were still tough as boots at that mark. Gave them another full hour and they finally turned into that fall apart tender goodness everyone wants. That extra time makes all the difference between chewy and perfect. My guests would have been eating leather if I stuck to the book.