Oh merciful heavens, the whole point of balsamic vinegar from Modena, Italy is that is stays in the family for decades, passed down literally over generations. To be the real McCoy, traditional balsamic vinegar of Modena must be at least 12 years old, but it can be several hundred years old.

Real balsamic vinegar is made by boiling down Trebbiano or Lambrusco grape juice to produce fermented juice, or must each fall. The vinegar is then aged in barrels of varying woods – including juniper, chestnut, cherry, mulberry, ash, and oak – which give it character and flavor as it moves from barrel to barrel from year to year. Over the course of the first year, as much as a quarter of the liquid evaporates. It loses less water in subsequent years as the liquid becomes more of a syrup. Once a year, the vinegar is decanted from the largest barrel to the next smallest and so on, a process that is overseen by an expert from the balsamic vinegar consortium. For all the work involved, small family acetaia (vinegar makers) might produce a half gallon a year.

One artisanal balsamic vinegar maker told Eric Dregni, author of Never Trust a Thin Cook that it is impossible to make balsamic anywhere but Modena. Why? "Oh, it's the air, the grapes, the humidity, everything." The Modenesi scoff at the industrialized version of balsamic, even though it can be a very good approximation.

Another man who makes a very good balsamic in stainless steel casks (his day job) and traditional balsamic (in wood on the side), became livid when explaining that a group of Neapolitans (almost 400 miles away) were trying to sell their vinegar as "Balsamic Vinegar from Modena, made in Naples." To be authentic, balsamic vinegar must be Aceto Balsamico Tradizionale di Modena or Aceto Balsamico Tradizionale di Reggio Emilia, which are products and names protected by Italian law and the European Commission. (It is the word tradizionale that is most often missing from copies.) The age of the vinegar is no guarantee that it is authentic or produced under the auspices of the consortium.

Now, unless you married into a northern Italian family (specifically from Modena or Spilamberto), or received a dispensation from a very lofty power, what you have is not Aceto Balsamico Tradizionale, but a commercially produced approximation.

Most of what is sold in this country as balsamic vinegar is regular wine vinegar with caramel color and sweetener added. Makes you hopping mad, doesn't it? It is probably not a very good approximation of balsamic vinegar, though you can find good balsamics, great balsamics, and if you hunt aggressively or marry well, the traditional stuff.

Very long way of saying, no, vinegar does not expire. That is one reason regular vinegars have been used for years to preserve foods for long storage.