What do you all think about the idea of a 'point' system with AP's? Every time you use your AP(entrance, purchase of some item(s)) , you notch up a point amount of some sort. Entrance would be a flat point amount but the amount of point you acquire for purchase would vary according to the amount of your purchase. Hence, bigger purchase, bigger points.
When you get to a certain level, you can use it to 'cash out' on a purchase or you can use it to help in the renewal of your AP the next year.