So....this is what I did with the '83 Taylor:
Carefully poured the contents of the bottle into a decanter. Leaving substantial amount of sediment in the bottle.
Then, I cleaned out the bottle and poured 3/4 of the wine back into the bottle, replaced the cork with a new one and placed back into the cellar.
I decanted, without a stopper, the remaining 1/4 of a bottle for 8 hours.
The nose slowly emerged during the decanting process, though the flavor didn't change much. It was very nice, though a bit lighter and more subtle than I would have expected. I drank one glass worth at that time.
Then, I left the remaining small amount in the decanter overnight. Eventually, I drank it after what turned out to be 24 hours in the decanter. The nose was much stronger, in a positive way, with raisins, sweet dark fruits at the forefront. The flavor was much more evolved, adding depth and complexity as well as length. Still, not a top level Taylor, but a good one. 89 points.
What does the amount of decanting tell us? I have no idea.