Enjoy the ride. My limited experience suggests your main source of agita would be SEA-ANC-SEA. They'll probably say "You're out of synch. We can't print your boarding passes because the computer doesn't think you're actually here in Seattle right now since you're due to arrive here from ANC later." I'm guessing you'll get the rest of your BPs in ANC. You might do better with this thread in the MR forum. Those hardcores could probably give you a more definative response.