I had a wild hair last season, and was about to take a run at a JMT fastpack in Sept. When I called MTR, they told me that they would not be open, or have any re-supply available after Sept 19. That was the cutoff day. I was thinking about trying to get there before then to take advantage of "free food" and re-supply to get thru the southern half. But my schedule didn't work so I bailed on the trip...
It was also posted on their website.