title_body: What are the factors that determine how long whisky is aged?
upvoted_answer: Aging or 'Finishing' is an extension of the maturation process, when the spirit is subsequently filled into empty casks that previously held other
  wines or spirits for a further relatively short period at the end of maturation.
  
  
    The selection of casks can affect the character of the final whisky.
    Outside of the United States, the most common practice is to reuse
    casks that previously contained American whiskey, as US law requires
    several types of distilled spirits to be aged in new oak casks. To
    ensure continuity of supply of used oak casks some Scottish distilling
    groups own oak forests in the US and rent the new barrels to bourbon
    producers for first fill use. Bourbon casks impart a characteristic
    vanilla flavour to the whisky.
  
  
  so really the longer you age the whiskey the more of the flavor you are going to capture form the cask