I've brought up tea storage vessels before. It's true that farmers and producers that I've met say that thick-gauge plastic bags have been fine for them, although most don't intend to age the teas in them for decades. Tea experts also carefully re-roast/refresh the teas every so often.
The consensus is that good tea goes into a vessel. Where the disagreement occurs is what type of vessel to use. Many people use clay or earthenware pots that have several layers of cloth or some other type of semi-permeable covering over the opening. Porcelain, glass, metal, coated tins, and certain types of rock also have fans that swear by them.
Just like prepping clay teapots, I think that storage vessels should be prepped as well. Washing is a given, and boiling or hot-water treatment may help. Once that's been done, though, one last step that I've been recommended to do is to use a tea product to absorb moisture and off-odors from the vessel. The product of choice?
Why stems? Aside from their cheapness, roasted stems are good at absorbing odor. It's exceptionally dry and has a surface area that is made to absorb and transport (water and nutrients). Yes, I know, it's dried and dead, but it's still pretty effective with moisture and smells. If you don't have stems, put in some decent grade tea. If it's old and musty tea, you can use some kind of tea freshening method on it first .
After a few days with the stems inside, toss them away, wipe down the vessel and it'll be ready for use. I put a good oolong into the clay jar above and it turned stale and lost flavor - wrong choice for that tea. I just picked up a nice, green puerh brick that should do nicely, though. Happy to report that I found something to put inside the clay jar!
Regarding pewter, which is one of my favorite container types, one must be careful of where it's produced. Cheaper pewter products from less-reputable producers can contain high levels of lead, which may leach into the tea and damage both the tea's flavor as well as one's own health.