If you store tea in the right way – away from sunlight, high temperature and moisture, its freshness will last longer and the good flavor will be preserved. The shelf-life of tea also depends on the tea type.
White and green – 1 year
Oolong – 1-2 years (sometimes longer if it’s truly a good quality oolong)
Black – 2 years
Pu-erh – is the only tea that can be exposed to air and improves its flavor and quality with years
Herbal/Flower – varies, some flower teas can lose their freshness even after 2 months
The more oxidized the tea is, the more prone it is to be affected faster by different factors. All teas are different however and for example Gunpowder, which is tightly rolled will hold longer then any open-leave tea. Tea may also take on odors from other foods, so it’s good too keep it away from the stove area (as it will absorb the steam and flavor) or anywhere where you keep your food supplies. Caddies and tin canisters are not necessarily 100% airtight, so as a percussion you can put the tea into a ziplock bag before putting it into the caddy.
Some green teas can or even should be refrigerated, because they contain about 6% of water. The refrigerator is ideal for long-term green tea storage, as long as moisture as well as aromatic foods are kept away from it. If you have your tea in the refrigerator and you want to take out a batch you should let the tea warm up first, before opening the container. Otherwise moisture from the air will condense on the tea leaves.