I am not knowledgeable about alcohol but it seems very unlikely that it would be still drinkable.
Distilled spirits have an unlimited shelf life.
As a retired professional drunk I can tell you that alcohol does not go bad in storage. It is a first class antiseptic and will kill microorganisms on contact. White spirits (alcohol straight from the still) is aged in charred oak barrels or Sherry casks for five to more then fifteen years. This is done to add color and flavor to the spirits, it also serves to mellow the flavor of the raw spirits by removing 'fusel oil', a more toxic byproduct of distilation. Once the whiskey is bottled in glass no further improvement is forthcoming. There is a possibility that bottles sealed with only a cork and stored at a higher then normal temperature (an attic) will undergo an evaporation loss (the Angel's share) which would alter the subtle flavor elements.
Regards,
GtG