weed can stay in your system that long if you don't know much about your system. if you know how to enhance the cytochrome p-450 enzymes in your liver by drinking polyphenols, which vitamin must be taken every day to make sure both phases of your detoxification system have enough electrons to support the elimination of toxins, and a certain clay to drink that removes toxins from your body and is inert (which means you don't digest it) so it can't show up on an urinalysis. I did 5 years of parole, smoking weed just about every day, and I passed all my piss tests. With the right program, Cheech and Chong could get clean overnight.