In theory, G+ return times get later and later at an incremental pace. This, of course, is dependent on demand. Slinky will sell out in minutes. Pirates of the Caribbean will take much longer. What happens in the mean time is a people cancel their selections. This is why at 11am, the next selection will be 2:00pm, and you refresh and it shows as 12:30pm, then back to 2:05pm. The cancellation gets put into the pool until someone grabs it. If you are too slow, you will see the 12:30 selection, but by the time you press the button, someone else grasp it a microsecond before you and you get stuck with 2:05pm. The chaos really occurs at 7am when everyone is picking at once. But later in the day it becomes more predictable unless you refresh long enough and get one of those cancellations with a more favorable time.