Aged Whiskey has gone through the majority of its chemical changes during barrel aging. It has been oxidized and condensed. The final product is generally stable, however further evaporation of liquids will occur over time just as in the barrel aging process, so storage in airtight containers would be recommended.
Sunlight has been known to increase the amount of substances like hydroxymethlyfurfurals in stored alcoholic beverages like mead and wine. I have not read any studies in direct correlation with whiskey, but with residual sugar present the production seems likely, thus storage in darkness, or non-UV light would also likely be a positive for long term storage.
Whiskey's shelf stability, especially if sealed, will bypass that of wine providing one of the most harsh environments for any sort of spoilage organism to take hold, with it's high ethanol content, as well as being more acidic than many more neutral liquors such as vodka.