OK, nevermind, I found this answer in an old thread....
Chip wrote:It is very complicated storing open tea in the fridge, and a little risky. I pull it off though, but most vendors shudder at the notion. I use a small tin (sample tin from Upton) for my everyday use, and bundle the reserve up to prevent loss of flavor. The tin I do not put in the fridge. The reserve I do, but do this at your own risk. If you do not store it in the fridge, once open, use your sencha within 1-2 months.
Remember also, when you take tea out of the fridge, allow the entire contents to warm to room temp so when you open it, moisture does not condence on your leaves.
Matcha, until you are ready to use it, store it in the fridge. Once open, it is too much of a pain to store in fridge because you have to allow it to warm to room temp each time you open the tin. Just use it in 60 days.
One more thing, before I put tea in fridge for cold storage, I always add some layers to it. Foil zip bags that vendors like Upton use are great for this, but in a pinch, use zip locks.