You would have to have much more information to know. First, what is the average storage temperature, and how much variation is there from the average on both a short term and long term basis. I would be very unlikely to buy any wines that had been stored at an average temperature of much over 60 F for up to 20 years. Also I would not want to buy wines for which the temperature varies over more than a very few degrees over a day.
The next thing depends om the specific wines. Some are not made to last up to 20 years and would have declined even under ideal storage. You mention Rothschild. There is Lafite-Rothschild and Mouton-Rothschild that will sometimes improve for well over 20 years with good storage. However in light vintage years they may not improve very long. Some Caliifornia Cabernets can last well over 20 years with good storage, while many others will be in decline. For example, even a 1961 Mouton-Rothschild or a 1959 Lafite-Rothschild should be outstanding with proper storage at under 60 F with little short term temperature variation. However many Bordeaux wines from 1984 might now be far into decline even if stored correctly.
It is a sad fact that many collect large cellars of wines, but do not store them properly and do not keep track of when they are ready to drink. Nearly any wine auction house buyer can tell you horror stories of cellars that would be worth $US 100000. if the wine had been properly stored, but that are nearly worthless because of poor storage. Someone who knows some of he wines for sale needs to taste some of these wines. An auction house would insist on tasting some to avoid buying storage-damaged wines.
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