As for Hawaii fares getting cheaper a day or two before departure, AS probably has a few empty seats and opens them up for FF award travel and low "last minute" fares. They are obviously taking the approach of having higher fares further out, seeing if the seats sell at the higher fares, and then releasing them at the last minute if they don't totally sell out.

That said, during peak periods, the fares often do NOT come down right before departure because AS has sold all the seats. So, I would not depend on being able to get a lower fare (or credit for a future flight).