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.
According to the Australian Tea Tree Industry Association, the shelf life of tea tree oil is around 6 months after it's opened, and up to two years when unopened. There are a few conditions though to keep in mind though. Tea Tree Oil, and most other essential oils like it cold. Think Tea Tree Oil on the rocks. You can significantly extend the shelf life of most essential oils by storing the oil in dark amber or cobalt blue glass bottles, or in stainless steel or lined aluminum bottles. Never Store Tea Tree Oil in Plastic...Ever!