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.
Most people would say 1 to 5 days. If the tea is sweetened, then it will be close to 2 days before it does not taste fresh. If the tea is unsweetened, it is said to last a dayâ¦ or so more. However if tea is not sweetened and has a sprig of fresh mint added to it during brewing, it can last 5 days or more.