How long does it take for upgrade eligibility to be restored after canceling an online order?

Sorry if this has been asked before, but I didn't find an answer anywhere. I have ordered a 16GB black iPhone 5 from the Apple Store online via an AT&T upgrade discount with a shipping date of Nov. 8th. I was content to just accept my lot until I saw last night that an Apple Store two hours away got some in stock for pick up. Now I'm thinking that a shipment or two might trickle in to my local stores soon. My question is - how long does it take for the Apple Store website to process your upgrade discount restore once you cancel an online order? Can I buy it through online pick up and then just get the discount refunded later? Has anyone had experience with this before? Thanks!