How long does THC store in your fat and muscles?
It is important to know how long things last in the human body. Easily detectable quantities of THC usually stay in a human body between 3 day and a months time. It is excreted more or less following the "half-life" model, i.e about half of it leaves your body during the "half-life" period of time. After twice that time 3/4 will be gone (½ + ½ of the remaining = ½ + ½·½ = ½ + ¼ = ¾)
It continues to leave your system this way with about 1/2 leaving your system during each half-life period. Eventually what's left is so small as to be insignificant and not detectable. Obviously the more you start with in your system, the longer it takes to remove what's there.
Keep in mind that even though the THC stored in your tissues will be depleted over time, the THC that gets incorporated into long-term structures like your hair DOES NOT. If you had THC in your system when that part of your hair was growing, it will be in that part of the hair and STAY there.