THC disappears at a rate of 3.83, 5.38 and 6.92 percent per year over two years when stored at 0, 39.2, and 71.6 degrees Fahrenheit, respectively. The loss of THC is essentially complete at 98.6 degrees. (http://www.unodc.org/unodc/en/data-and-analysis/bulletin/bulletin_1997-01-01_1_page008.html)