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.
If you donât notice a difference in flavor when you keep tea in the fridge for longer, then by all means keep it for as long as it tastes good to you. With one caveat: itâs probably only safe to keep it for a week at the most. Iâm not an expert on bacteria growth in tea, but a week is generally how long most prepared foods can be kept in the fridge before discarding them.