at what point will they cut off pavillion access?
if all tickets say GA on them, they will give out enough wristbands, on a first come first server basis to fill the pavilion, the rest will have to be on the lawn, and you will need to show your wristband each time you enter the pavilion.
so buy your tickets whenever, but get to the show nice and early that day, to ensure a wristband for the Pit or Pavilion.
thats how its been done in the past anyway.