How long does box wine last?
One of the huge advantages of boxed wine is that it lasts for a month or even more after being opened. This makes it very practical for glass-a-day drinkers who would find storing partially opened bottle wine problematic or wasteful. But, box wines aren't perfect - it turns out that the bag-in-box packaging is very slightly permeable to oxygen, and after a period of time the wine will oxidize and darken.
Most box wine makers use about a year for their "sell by" date. If they bottle it, or, more accurately, bag it, in October, they allow it to be sold by the following October. They do, however, assume that the wine will be consumed shortly after that. An interesting article in the Austin Chronicle quotes one bag-in-box supplier:
"Our Quality Control department has run extensive tests on the 3L package (i.e. box wine) which show that the wine stays fresh for 14 months," said Holly Evans, director of public relations. "However, we feel it best to be conservative and go with 12 months."
Not everyone is that generous. Devon Broglie, a master sommelier who works for Austin-based Whole Foods, said that after Whole Foods conducted an extensive test of boxed wines, preferred six months as the sell-by date.
What does this mean for the box wine consumer? If the box is within its sell-by date, it's probably fine. If it's many months from that date, so much the better. The important thing is to not pick up a few boxes on sale and let them sit for a year. Boxed wine isn't like fine wine in bottles - it's not meant to be aged, and it won't get better. In fact, the nature of the packaging means that a box that's a couple of years old or more has probably deteriorated to some degree.
So, when you shop, check the dates, and don't stock up on more boxes than you will consume in a month or two.