On another thread we were discussing the effect of cork vs screw closure in aging wine and something occurred to me.
When Bourbon is to be bottled it's first dumped (literally) from the barrel by rolling the barrels along a trough, pulling the bung, turning the barrel on its side and the contents come tumbling forth mixing with air on their way to the vat. In the vat aeration continues with water being mixed in to bring the barrel strength spirit down to bottling proof. The filling line further mixes in air with the tubes that fill the bottles.
So when a bottle is finally sealed with cork or closure a certain amount of oxygen is going to be trapped inside. As it's generally agreed oxygen is the catalyst in the aging cycle when Bourbon is in the barrel doesn't it stand to reason the trapped air in the bottle is going to further the process a bit, or that a less than perfect seal may have some effects in the long term.