PG Evaporation from Gallon Bottle?

[PaulB]

I bought a gallon jug of U.S.P. PG about six months ago and dispensed some into smaller bottles for mixing. As I recall, that didn't make much of a dent in the gallon. For the first time in a while, I looked at the translucent plastic gallon bottle and noticed it's down way below half. Either I'm being forgetful (either in how much I've dispensed/mixed/vaped or maybe I mistook it for vinegar or something else we keep around in that size bottle), or PG kept in that type of container evaporates pretty furiously. Knowing myself, I may not have screwed down the cap tightly enough--but we're talking a LOT of disappeared PG. Has anybody here had a similar experience?