Last year they were on separate pages according to my DD as I had told her about the "trick". I dont know if this is 100% correct but that is how she saw it and I think under exam conditions its a little nerve wrecking for them to remember doing something diff to what the invigilator is saying.
As scarlett say you dont need to finish all the questions. My DD never had problems with completing any papers. She would finish ALL her papers and with a few more minutes to spare in most cases (and boast at home how fast she was and had 10minutes to spare) but she wasnt succesful. Being fast sometimes mean they can miss some key bits particularly in NVR so it isnt always a good thing to complete the paper in time.