Originally Posted by
JDP
What is left of the government could have been maintaining the relays for months and even years, no way of knowing. What we do know for a fact is that they "used to talk to Washington all the time" until relatively recently, that's why they are pressuring their radio man to attempt to reestablish contact, which is why he complains that the equipment at his disposal is not adequate to do that. These guys have not been in such isolation for a very long time, they were up to date on what was going on in other places up until relatively recently, and their outlook on the situation is a very pessimistic one. Obviously the feedback from their bosses in Washington was not encouraging at all.
That's the first time they explore that particular area by helicopter, that does not mean that they haven't been doing other explorations, either by chopper or on land (they got plenty of land vehicles at the base.) We can easily deduce that they in fact have been doing just that. When they arrive at the base after visiting the dead city, Miller sarcastically remarks: "another waste of time, huh?", to which John replies "got that right, man!" From their previous explorations, Miller already anticipated that this one was also going to be a failure. Also, when they are at the dead city, John tells McDermott that: "It's a dead place. Like all the others, you know". Again implying that they have been looking around, but have found nothing but zombies.
The operation itself was put together hastily, but that doesn't mean anything regarding how much time it has actually passed since the events in Night, though. Their bosses in Washington could have planned it in just a few days but many months or even years ago! Sarah is referring to the fact that the operation itself was not well thought out and put together in a short time, she's not saying that they only have been there in the bunker for a few days. Also, considering how many zombies they had captured and brought down to the cave area, I would say that it in fact took at least several months to actually accomplish just that task alone! They had to go up to the surface, round up, capture and restrain zombies that were roaming free, then bring them down and free them in the cave system. Before that, they obviously also had to make sure that the caves were isolated from the main underground complex and also eliminate any other possible exits (minus the missile silo, since zombies are too clumsy to climb such a tall ladder, so no need to block that one), otherwise the zombies would have found their way out. When you consider all such details, it becomes pretty obvious that these guys have been in this bunker for a good while.