hades65 said:
In theory the cannabinoids do degrade but I have been vaping on mine for 3-6 months and have not noticed a difference. Not to say there isn't a difference, but I think your experience probably has something other than your weed going bad. I think the degrading process is a very slow and long time. Anyone have any statistics?
Here you go:
http://www.skunkskool.com/showthread.php/5128-Degradation-of-Cannabis-and-THC
Degradation of Cannabis and THC: Storage Methods and Mold
Erowid
Constituents of Cannabis sativa L. XIII: Stability of dosage form prepared by impregnating synthetic (--)-delta 9-trans-tetrahydrocannabinol on placebo Cannabis plant material.
Lewis GS, Turner CE
J Pharm Sci 1978 Jun;67(6):876-8
Abstract:
Synthetic (--)-delta 9-trans-tetrahydrocannabinol impregnated on placebo Cannabis decomposed only 6.3% after being stored for 1 year at --18 degrees. Storage at 5 degrees and room temperature under various conditions led to severe decomposition. The amount of cannabinol observed when (--)-delta 9-trans-tetrahydrocannabinol decomposed indicates that cannabinol is not the only decomposition product.
This one explains why I state you should vape your herb at one time in a short session instead of extending it to days after or maybe later on in the day. You can still get high but not as you would if you just vaped all the herb right away. Vaporizers provide the perfect environment for degradation, air and heat.
The stability of cannabis and its preparations on storage
Fairbairn JW, Liebmann JA, Rowan MG
J Pharm Pharmacol 1976 Jan;28(1):1-7
Abstract:
Solutions of pure cannabinoids, nine samples of herbal and two of resin cannabis (one freshly prepared) were stored in varying conditions for up to 2 years. Exposure to light (not direct sunlight) was shown to be the greatest single factos in loss of cannabinoids especially in solutions, which should therefore be protected from light during analytical and phytochemical operations. Previous claims that solutions in ethanol were stable have not been substantiated. The effect of temperature, up to 20 degrees, was insignificant but air oxidation did lead to significant losses. These could be reduced if care was taken to minimize damage to the glands which act as "well filled, well closed containers". Loss of tetrahydrocannabinol after exposure to light does not lead to an increase in cannabinol, but air oxidation in the dark does. It is concluded that carefully prepared herbal or resin cannabis or extracts are reasonably stable for 1 to 2 years if stored in the dark at room temperature.
This goes more in depth:
http://www.unodc.org/unodc/en/data-and-analysis/bulletin/bulletin_1997-01-01_1_page008.html
Just use a vacuum seal to keep material fresh as much as possible by keeping air out and put into dark containers and in cool places. There all types of machines that pump air out of containers.