I bought my Premium AP 9 days before I left on my trip. The AP centre in DL is on Main Street on the left hand side past the Carnation Cafe, and directly across from the Plaza Inn. The AP processing centre in CA is in the Greetings from California store just inside the enterance. What I did when I arrived at the parks the day of my arrival, was that I saw the lineups to get into DL were really long, so went to the CA ticket booth, and showed them my E-ticket. They gave me a plastic card, and was directed to the Greetings from California store, and less than 5 mins later had the AP and was hunting for a place to eat lunch. It's that simple, and even though I bought my AP 9 days before I arrived, it's start date was the date I arrived and entered the parks for the first time. I thnk the e-tickets are good for at least 40 days before they expire, so you've got lot's of time to exchange them before they expire. Hope that this helps you out.