Matcha won't "spoil" after that time (assuming no moisture got to it)...it simply won't taste as fresh or look as vibrant. Though matcha is dried, it can still be damaged by oxidation and UV light if exposed to air or sunlight for too long.
This is why any matcha container must:
1) Be airtight! Both our zip lock style pouches and screw-top tins can be closed securely to create an airtight seal.
2) Block UV light. Our pouches actually contain an aluminum foil liner that blocks all UV sunlight from passing through. Our metal tins do the same.
3) Avoid heat. It is ideal to store your matcha in the refrigerator or freezer between uses.
Now if you're like me, you think "the pouches are great, but sometimes I wish I had a reusable canister that was easier to scoop out of." And after a little research, I found three available on Amazon that pass the above tests (and look great too):
Made of a special type of glass that blocks out all UV light. This jar should hold about 100 grams of matcha. Link.
Latching Tea Tin ($9.40)
Nice latching style means you won't ever lose the lid! Holds about 200 grams of matcha. Link.
Screw Top Canister ($19.95)
Simple design made of stainless steel. Holds about 250 grams of matcha. Link.
So now that we've got our matcha stored all nicely, let's get to a tasty recipe to actually use it in!