Should Cognac be cellared upright or on its side?

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Dear Dr. Vinny,
Should Cognac be cellared upright or on its side?
—Phillip C., Malaysia
Dear Phillip,
I’ve fielded a couple Cognac questions in the past. If you’ve never had it, it’s a brandy made mostly from the Ugni Blanc grape.
Unlike some fine wines, Cognac isn't intended for aging. Once bottled, Cognac stops maturing, which eliminates the need for long-term storage. That said, it can also last a very long time.
Even though many Cognacs use a cork for a stopper, the corks are often topped with a plastic or metal cap, which helps prevent the cork from drying out. The consensus is that Cognac can be stored upright in a cool dark place. No need to store it on its side or rotate the bottle. Once opened, the contents can evaporate slowly and the flavors fade, but you probably won’t notice any change for months.
—Dr. Vinny