Currently batches will always print using whatever settings the author had when generating them. This means if you had accidentally left your labels set to 8.5 x 11", but needed to print a batch of 381 labels using 4x6" labels, you'd need to void out the entire batch, remake it, and print it. It seems much more intuitive that these labels respect the current user's settings.
I understand this was implemented this way to essentially cache the labels on your server for a better user experience. If that is a concern, what about some option to force generation of the labels again, instead of using whatever was generated at the batch's conception?