As I said earlier, becareful with buying from stores. I work in retail and after Issue 6 or so we stop getting in partworks, as they go from sale or return to firm sale only. Now different retailers might operate a different policy, and the US retailers might be different from UK retailers. But I would recommend you either subscribe or speak to your local retailer when the first issue comes out and ask them if they will continue to get it in.
Bear in mind retailers only have limited space and plenty of partworks come out, they can't possible keep getting in copies of them all in.