Here in Raleigh, NC (about 175 miles west of VFT country) we had a month
without rain in the hottest part of the summer (July & August). I went to
look at the VFTs not long after that and they were still doing fine.
True, they were in the Green Swamp which is an enormous peat mat floating
on top of underground water, so the peat there should always be a little
wet. But I think the moral of the story is that VFTs can probably handle
it drier than most people keep them.
Phil