What's the shelf life of a box of wine?

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Dear Dr. Vinny,
What's the shelf life of a box of wine?
—P.M., San Antonio, Texas
Dear P.M.,
Good question, as there definitely is a shelf-life for boxed wines. There is a bag inside the box that holds the wine, and it cleverly collapses as wine is consumed, limiting the wine’s exposure to oxygen. That means that once you open the seal and start pouring the wine, you should be able to enjoy it for at least a few more weeks (as opposed to a few days with an open bottle) before you notice that the wine is fading. In both cases, storing an open container of wine in a fridge will extend its life.
That bag is typically made of polyethlene, which is a very safe plastic to use, but it’s not as impermeable as glass, and over time, the microscopic amounts of oxygen passing through will cause the wine to lose its freshness. If you look at the box, somewhere on it (perhaps on the bottom) will be a best-by date, usually about a year from the date it was packaged.
Given all of this, the wines inside the box aren’t meant for long-term aging. But there are some terrific wines in boxes. When we review boxed wines, we review them in blind tastings alongside their bottled peers, and we find plenty of wines to recommend.
—Dr. Vinny