Unlike wine, whiskey does not continue to mature once it's in the bottle. If stored properly, a sealed bottle of whiskey can remain more or less unchanged for hundreds of years! Once you've uncorked it, your whiskey will begin to slowly oxidize, but you can still extend its life by keeping it in a well-sealed container away from light and heat.
Exposure to a lot of light—especially sunlight—sets off chemical reactions that will both discolor your whiskey and affect its flavor. Keep your whiskey in a dark area, such as a wine cellar, cupboard, box, or darkened pantry.
Temperature fluctuations, and especially exposure to heat, can affect the quality of your whiskey. When whiskey gets hot, it expands in the bottle, which can eventually damage the seal and let in oxygen. Keep your whiskey in a cool, temperature-controlled room or container.
Always keep your whiskey bottles in a vertical position. If stored horizontally or upside-down, your whiskey will constantly be in contact with the cork, eventually causing the cork to deteriorate. This can affect the taste of your whiskey and allow oxygen to leak into the bottle
Sorce: wikihow.com