Is the game length the time the table is secured?

what happens if the game goes longer?

If the table is not booked for the next top of the hour or time slot, then you would be fine to keep going. However, if there is another game scheduled, you would have to end the game or try to find another table maybe working with that area's HQ or in open gaming area if available.

More than likely, other players or even the GM are also booked or need to move on to something else as well based on the time scheduled.