You know that is a very good question but I do not know. We were there around the same time as you and I did buy a bunch of those pictures. I was surprised at how well they turned out- wasn't planning on getting any.
So for those of you going down, check out the pictures. You are under no obligation to buy them.
Not sure how long they keep them. But I do know it is hard to find them after the second day because of the amount of pics they take daily. The first thing we do now is, go look at them and wright the time, date, and pic number down so they are easily located. It definitely helps.