If you see something you want, you should probably go ahead and buy it. I've been going about every two weeks since mid-December and the merch options seem to be different every time (I'm not necessarily talking about 50th stuff, though). I was debating buying the Kate Spade 50th Anniversary mini backpack when I was there for the Marathon Weekend; it was pricy, so I told myself that if I finished the marathon, I'd get it. I finished the marathon but wasn't able to get back to the shops until two weeks later, and they are now out of the backpack and say that they probably won't be getting any more in stock.