Are you really popular enough for me to answer this question?

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The expiration dates are really more of a suggested best-used-by date. There are components of juices, water specifically associated with the flavorings that could cause a degradation in taste. Many folks on the board have and use juices that are well past their noted expiration date. As for bacteria etc., no...that shouldn't be an issue as the PG/VG would take literally forever to breakdown and are not good hosts for bacteria due to being alcohols.
I hope that helped....
Add edit: Morandir....good morning! Fancy meeting you here.....hehehe
Funny, I was gonna get into the details of "head space" half bottle v full bottle etc. etc. but it seemed like it might be a little information overload.