Any advice on how to store black tea for aging?

I would just put tea in some mason jars and leave them in a cool place away from light.

There’s nothing like opening a forgotten jar after a few years and enjoying the aroma.

Black tea is already “oxidised” so it’s really made for the long term.

On the other had, a white tea will continue to oxidise over time. Bai Mu Pan (off the top of my head, is a good example.

The leaves to make matcha (Tencha) are usually aged from spring and drank in the fall / winter for a more robust taste.