Does expired tea lose its health benefits?

If it's already steeped and in a liquid form and it's expired, I would not suggest drinking it!

However if it is merely the leaves, and depending on what tea it is and if they have been stored appropriately, the health benefits did not just dissolve into the air. There are still health benefits, although they are 'diluted' slightly, and there's the risk if you did not store them or if they are old enough, there could be mold and other contaminants in the leaves.