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.
Green tea does not require much time. Too long a steeping time will result in more bitterness and a less balanced flavor. We recommend experimenting with a range of 1 - 3 minutes. Japanese green teas generally taste best at 1 - 2 minutes while Chinese green teas seem to prefer 2 - 3 minutes (the smaller leaves of Japanese teas will extract faster than the generally larger leaves of Chinese teas).