Hi Christian, Yes it does, but it also gives flavor to the wood in turn, So a first and second fill bourbon barrel will give its bourbon flavors to the spirit maturing inside of it, depending on the age spent for maturation, a third fill cask will give litlle bourbon/sherry tones to the spirit, all it has left to give is wood, matured wood at that.After 30 years i simply cannot imagine what a third fill cask can give else then that.
I think I didnt made a clear point come to think of it, a first fill bourbon cask would indeed give woody flavors to the spirit, those flavors will transform in other flavors with time, mainly floral notes and vanilla's. an example: many of the young malts (3 to 7Y) have at least hints of liquerice in them, especially on Cask Strength, thats what i call "young wood" and usually they are accepteble in the overall flavor, but too old malts have this musty oak, worn out wood/wet wood taste written all over their flavor profile effectively drowning the other flavors.
You can get the exact thing with "too young" malts too, i know, but its a completely different flavor, its strong, overpowering new wood, often with a rubber tone alongside.
To get to the point, the first wood tones a cask infuses to the spirit is admirable, necessery even, all in all, good and positive.
After 2 fills and during the third fill the wood gets tired and releases little or no more of the so needed vanillas and lactones wich are needed for the interaction and flavor exchange with the spirit so it has nothing more to offer then worn out wood to the already complex and delicate spirit after all these years.
However, like I said, this is a theory explained to me by only a few but one I believe at this point. I am doing some research about it along other things and am still awaiting reply.