From Michter's:

While we regularly sample all our Michter’s barrels to see how our whiskey is aging, we pay even extra special attention to our barrels once they are over 17 years old. At Michter’s we consider 17 to 20 years the “Fork In The Road Point” when certain barrels of whiskey can achieve an extraordinary level of quality. It is these particular barrels that our Master Distiller Dan McKee personally selects for our very limited bottling of Michter’s 20 Year Kentucky Straight Bourbon.

*This is the 2019 Bottling*