We've been emailing recently about the aging of Port vs. Madeira and here was an excellent analysis of his that I'd like to share. Hopefully, this topic will raise other questions and commentary from YOU.
If I recall they were all bottling between 18 to 24 months to free up cooperage for the coming harvest. The main point I was trying to make is that vintage port is "reduced" (the opposite of oxidized) compared to Madeira when it is bottled and that is why Maderia and other wines made in that fashion do not change in the same way after bottling as does vintage port.
The development of the wine in barrel is different from that in bottle because of differeing rates of oxygen uptake. Barrel aging allows for controled rates of oxygen pickup whereas aging in bottle is nearly anerobic. This results in preservation of fruit flavor, much slower polymerization of polyphenols and importantly, the development of bottle bouquet.
To my taste, vintage port is best enjoyed before it has turned tawny; and there is still fruit flavor. There is definately a point where the phenolics have pretty much precipitated and the wine is left with no protection against oxidation and where it begins to oxidize more rapidly, loses its fruit, and starts to taste hot (more alcoholic).
Many of the ports older than 1955 are already at this point, in my view. I went to a tasting of 1955s last December and those wines didn't need any more aging.