You might metabolise 1 unit per hour, though it might be very much less
True, although I'm under the impression that the effect is cumulative meaning that 4 units could take considerably longer than 4 hours to metabolise. Clearly, 12 hours (or greater) bottle to throttle is an unscientific and very rough rule of thumb following fairly limited intake.
Nevertheless, with the potential for detection being greater these days anywhere, I would have thought AMS where checking at the crew centre has been in place for years has got to be the one place where abstinence on a night stop would be prudently observed?