For fear of cork taint, I minimize stirring bottles. I'm thinking this is a mistake. I've noted that premium bottles often are best when new and that as they age they lose complexity. At first I assumed congeners lost to evaporation or air oxidation. Many members on this board noted that flavor profile doesn't dramatically change till getting to about bottom 5th of bottle so many assume oxidation is not a big deal.
Well, I've been working on a different theory and my latest sip of Woodford may corroborate. I was down to the last dribble of Woodford and the flavor was the same sweetness as expected. BUT then I poured the last shot and kapow, bitterness like drinking their Maple Finish. What happened? Same as the loss of complexity of the premiums!
Density!!!! Many of the congeners (aka complexity) are lower density and will rise in a stable bottle. Many of the tannins and other material are higher density and will sink in a stable bottle.
This raises another issue. Profile change from top to bottom of a barrel if a barrel is not shifted before dumping. Maybe this explains why a recent ER10 was nasty, but the ER10 I'm now sipping after the Woodford is Stagg worthy.
--Note that this is a far different issue than what moonshiners have long known: flavor profile changes depending on early portion of distillation versus latter distillation. We're talking collecting entire distillation and mixed into barrels.