I always wanted to know how long weed stays potent enough to get a person stoned or just go bad. I was thinking like a year or two, but i found a cannie from like 4 years ago with some DANK in it and it was still good, not great but alright.
i found some 6 month old schwag that i had accidently left in my butane hash tube (free air, not sealed) and i was desperate, so i tried it. it had actually aged to perfection, whatever left over hash-goo had stuck to the dehydrated leaves made for a pretty decent experience. that's how i learned that making butane hash does not completely deplete all usable material from the leaf. as long as it's dried and cured properly, sealed in an air tight container, and then kept from light exposure, i've had friends that even after 2 years testify that it's just as good.
I don't like to keep it more than six months but it can keep for years with just small losses of potency if it's stored properly.