Fat Nick
Footballguy
Indefinitely I would think. It's all pressure treated lumber, so you'll be fine.
This. There's a common misunderstanding about water rotting wood. Water rots wood - but not from just getting wet, but rather from getting wet and being unable to dry. That's the reason flashing and such is so important for the ledger board. The ledger is isolated against the house - all things equal (i.e. with no flashing, etc) it wouldn't get any more or less water than any other part of the deck. It's more prone to rotting because it has limited breath ability if water gets between it and the house. It's also the same logic with why most of the time it's recommended to put a membrane over doubled/tripled joists or beams. The water can get in, but there's limited ability to dry out quickly.
A deck frame is PT, and if you tear the decking off, air-flow and ability to dry is actually BETTER than it would be with the decking on - it would actually most likely last longer without the decking than with as the decking would trap moisture against the frame.