I didn't see any price breaks through AAA when I tried to find one (put in our member #, used the special link and the prices were exactly the same ). If you are a member, maybe call them and find out? I ended up buying tickets for our upcoming trip from undercovertourist.com. The tickets from Costco end up being about the same price for 3 day tickets as the 4 day tickets I bought from UC, and I knew we'd use at least 3 days of tickets so the "unexpiring for 3 yrs" didn't appeal to me.
we got ours from Mapleleaf tickets, but Undercover Tourist also sells them at a discount (we got our DW tix from there). Just check them both and see which is best. Remember, they include tax and shipping...the price is the whole price.