I once had a 6.5lb butt take 26 hours but you have got me beaten-yours took five hours per pound, mine only took four. I don't think that any of us really know why. The larger butts all seem to be in the 1-2 hour/lb range and, imo, eat better. Cook larger butts, invest in a vacuum sealer, freeze and reheat leftovers. Leftovers are the laziest Q of all!