How slow is a ester reaction without a catalyst? (in a whiskey barrel?)
The best info I could come up with is from wikipedia (with no citations for the relevant sections)

https://en.wikipedia.org/wiki/Fischer–Speier_esterification

For reaction with an excess of one reactant and an acid catalysts, it says: 


  "Typical reaction times vary from 1–10 hours at temperatures of 60-110
  °C."


Later it talks about ester reactions in wine: 


  "Of course, when compared to sulfuric acid conditions, the acid
  conditions in a wine are mild, so yield is low (often in tenths or
  hundredths of a percentage point by volume) and take years for ester
  to accumulate."


Which is a bit of an Apple to Oranges comparison, and is not whiskey, but it gives an indication of 'Yes, slowwwwww'. Or something like that.