ALTHOUGH JUST ABOUT every wine in the world is created to be consumed within a year or two of its release, one of the most frequent questions that wine merchants field is "When should I drink this?" The reply can range from the vague (e.g., "anytime over the next decade") to the rather specific (e.g., "in 2016").

There's a great deal of anxiety among oenophiles about ideal consumption time, especially if it's a fancy bottle with a sizable price tag. Wine merchants are happy to offer advice—or...