the only way to do this promo, is to ALWAYS sign up for a new 2 year contract. so, it is a perpetual extension. One can't go into apple with a previous iphone and just get money and one cannot go into an apple store and get the trade in and apply it to an unlocked, off contract phone. So, this is basically the same type of program that verizon and AT&T have offered where you can always upgrade at nearly any time. IMHO, it's not the greatest of deals. From a pricing standpoint, you'll usually get a bit more money (like 15-20%) from a gazelle or craigslist, and then just do a bi-annual upgrade with a carrier or apple.