So, we were decorating the tree last night and -- whoa! -- needles were dropping. And the branches felt a bit dry. It's too soon to tell whether this indicates the trial was a failure, but in the interest of preventing a fire hazard, I filled the reservoir with water.
I'm reserving judgment, but I'll know more tonight when I get home and check the water level. If the tree's soaking up water, then the Vacation preservative isn't working; but if it's not, then that could indicate the tree doesn't need water, which could point to a success.
I'll post an update tomorrow morning.