Tea should be drank fresh. This is true for green, black, oolong and
white teas. The only exception is the Chinese black tea pu erh.
Classical "pu erh" or its subset "tuo cha" is kept for decades (like
fine red wine) in China until its taste is extremely mellow.
Exceptionally fine aged-pu erh is very rare. One of such pu erh tea
brick can cost $300+. You can find out more about tea at "Tea
University" at http://www.brandconcepts.biz/4teauniv_main.php.

Greg