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.
Generally, green tea can keep for about one year in an normal temperature, and for some Yunan pu-erh tea, it can keep for many years, the more years they have, the more pure taste they will be. If a tea has the following characteristics, so the tea can not be drunk any more: 1: Go moldy or stale.