How long will an unopened bottle of Champagne stay good?

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Dear Dr. Vinny,
How long will an unopened bottle of Champagne stay good?
—Barbara, Mt. Vernon, Va.
Dear Barbara,
Champagne and other bubbly wines won’t go "bad," per se, but they do age, just like other wines, which means their flavor profiles will evolve and, in the case of sparkling wines, they’ll eventually lose some or all of their effervescence.
The acidity and carbon dioxide will actually preserve a bubbly’s fresh fruit flavors for a while. Well-aged sparkling wines (in cool, dark cellars) will turn a darker color, and evolve into more dried fruit, nut and honey notes. You’ll probably notice a change at about the 10-year mark, at which point I’d expect there would be fewer bubbles too. Excellent vintage-dated sparklers will age even longer.
—Dr. Vinny