Years? How about centuries?
Centuries are made of years. Give the right conditions the wine is as good or better then when made.
There have been port wines that were over 150 years old when sold. Lots of private wine cellars around Europe, often very old casks and bottles are discovered in areas that weren’t hit hard during WWII. Spain seems to be a big source of the oldest such examples - that is also where the surviving bottles of “pre-ban” absinthe were found. A well-stored Madiera could indeed be suitable to drink, 200-odd years after it went in the cask.