Unopened wine box last

You did not ask "how long" you wonder if it lasts. However, boxed wine comes from a vacuum packed container. Air makes wine go bad, so boxed wine will last longer than opened bottled wine that is not re-vacuumed..

Avoid heat.

After the 1994 earthquake in Northridge, California, the wine purchased at the reopened Trader Joe's store was mostly bad. The building had gotten too hot without air-conditioning (in a mall) during the days without electricity.

So keep your boxed wine in a cool place, like a cellar or whatever the coolest room in your house is. If it's white wine, store in the refrigerator so it's ready to use.

Almaden Chardonnay 5 litres doesn't last long enough at my house, even in the summer, to go bad!