Reference
Tea Brewing Questions: Water Temperature, Steeping Time, Bitterness and How Much Leaf to Use
Delicate teas need cooler water; strong black teas need it hot. Most brewing problems come down to the same four things: the water, its temperature, the steeping time and how much leaf goes in.
Does Tea Go Stale? Shelf Life, Pack Dates, Tea Bags and How to Store Tea
Tea has no hard expiry date, but it is an agricultural product and it goes stale. The longer it sits, the more aroma and flavor it loses, until the cup tastes flat.