Well...

I have a little bit of some Northern Lights from a year and a half ago and it still rocks my world on the rare occasion I smoke it (I have Chrystal now, with some Durban PoisonxSkunk coming soon).

I keep mine in airtight glass jars in a cool, dark place.

Remember these three things about keeping your weed and maintaining its potency:
1) Store it in an airtight container
2) Store it in a cool place. I don't know anything about freezing or refrigerating it. Anyone with some experience as to how well that keeps it?
3) Store it in the dark. Light turns THC into CBD- the stuff that gives you headaches and short-lived buzzes. Just like heat does.