I'm not much of a drinker, and I noticed that even though I'd put the
cap on tightly, the level had dropped in one bottle. And what was
left didn't seem any stronger.
Another bottle had never been opened, but the level there dropped too.
It turned out that the paper or foil or whatever going 3 inches down
the neck of the bottle had come off the bottle and it was evaporating
without ever having been opened.
Neither cap would tighten until I squeezed it enough to distort it a
little. Before that, the cap threads were bigger than the bottle
Admittedly, it was years since I had drunk from one or gotten the
I think the lesson is, Drink more.