A tablespoon is a non-scientific but very widely used unit of volume, which works very well in cooking, herbal medicine, etc. It is represented by a capacity of one tablespoon which varies from roughly 15 mL in the US to 20 mL in Australia.
1 If tea is properly stored, it can potentially last up to a year for green and black teas. White tea lasts about six months before it isn't as good in quality as when fresher. Stale tea (or bad tea) will taste flat, as if you're drinking paper.  Glass or ceramic containers are fine provided that they're opaque.
On various websites I have seen loose-leaf tea blends with ranges from a couple months to a year for green tea and up to two years for most black teas. Thatâs quite a range. Prepackaged tea has an even longer useful lifespan marked on the box often up to three years. Tea Bag Storage. Prepackaged bagged tea remains pretty stable for quite some time if you take care of it. If the tea company tells you their product is good for three years, it will probably be good for a little while longer.