Keeping loose-leaf tea fresh at home

Loose-leaf tea does not go off, but it does go flat (sample note).
Keep it in an airtight tin, away from the cooker and the spice rack, and buy green tea in amounts you finish within a few months. A glass jar on a sunny shelf looks lovely and fades the tea in weeks.
Pu-erh is the exception: it likes a little air and keeps improving for years.