When asked about the lifespan of an open bottle of bourbon, Robyn Smith, a whiskey expert, told us it can last for years if “it's sealed tightly and kept out of heat and sunlight.”

"Bourbon is high-proof and shelf-stable,” she said. However, if you're drinking a bottle too slowly, you may start seeing signs of oxidation once you're halfway through, per Smith.

Indicators of oxidation include irreversible cloudiness and off-flavors. There could be a hint of sourness, or the spirit's original flavors and aromas may become toned down.