Good thing about a pellet smoker as opposed to a charcoal smoker is that it will maintain constant temperature even in the cold. But be sure to check your pellet hopper more often than you're used to.

I usually cook an 8lb butt for 12-12.5 hours at 225F. Halfway through, I double wrap in foil with beer and apple cider vinegar. Bone always comes out clean as a whistle. Meat stays moist.

What smoker do you have?