What is a common characteristic of spirits that have gone through extensive barrel aging?

Spirits that undergo extensive barrel aging often exhibit more complex flavors due to the interaction between the spirit and the wood of the barrel. During the aging process, various compounds from the wood, such as tannins, lignin, and vanillin, are extracted into the spirit. These compounds contribute to a rich tapestry of flavors, including notes of vanilla, spice, caramel, and toasted wood flavors, which would not be as pronounced in spirits that have not been aged.

Additionally, the aging process allows for oxidation and evaporation, which further develops the spirit's character and depth. The balance of these complex flavors can create a more nuanced tasting experience, making barrel-aged spirits particularly sought after by enthusiasts who appreciate the intricacies introduced by the aging process.

While acidity, body, and alcohol content can vary in spirits, they are not inherently defined by the length of time spent in barrels, making the development of complex flavors the most definitive characteristic of extensive barrel aging.