For the stoners who don't burn through all their weed in a timely fashion — and those who get so high they forgot where they hid their stash — the same question arises: How long does weed last? Does marijuana go bad?
Well, it depends what you mean by "bad." The fact is, no matter what some bro on a message board told you, weed is never going to expire or rot quite the way milk and meat does. It's also not going to get significantly less potent or age like a fine wine if you hold onto it for a year. Even so, you might say that weed has something of an unspoken "best used by" date.
When you buy freshly cured marijuana, there's a little moisture to the buds that makes them springy and squishy. Over time, depending on how you store it, weed will either dry out or become too wet. Plastic sandwich bags can let moisture out, with the eventual result of weed that crumbles and gives off harsh smoke. If you put your weed in the fridge or freezer, or leave it somewhere damp, it's apt to grow mold — and it sure won't burn well. Experts recommend keeping your stash in an airtight jar, at room temperature.
Naturally, desperate times call for desperate highs: Many people have rolled up dry weed crumbs (known as "shake") or scraped mold from weed before packing it in their bong. That said, there's nothing too pleasant about trying to get stoned either way — the taste will be awful, you're probably going to cough a lot and accidentally smoking that mold can have some nasty consequences, including headaches, vomiting and diarrhea.
All that is to say, if you find yourself questioning the age and freshness of your pot, do yourself a favor and just buy a new eighth.