Pu-erh tea, unlike any other tea, actually gets better with age. Made from either black or green tea leaves, pu-erh has an earthy, mellow flavor.
Honestly I've never even heard of this tea so I had to go look for more info about it. Most of the time a tea does not improve with age because teas rely on the remaining oil in the leaves (after the dehydration process) for flavor and strength. Tea doesn't always go "bad" but it will go stale as the oil will eventually completely dissipate leaving a rather bland taste if brewed.
I'm not sure HOW accurate the wiki article is but it's very interesting.
They say it's made in "bricks" which if you recall from earlier Tuesday Tea's, tea bricks were a common form of currency used in ancient Asia. These bricks haven't lost their value as some of the OLDEST of the Pu-erh teas have sold for thousands of dollars for just one!
I think I'll pass.