I have never seen any legitimate data on THC testing done before and during any extended timeline. However, I hope to do some very soon once my Cannalytics kit comes in. One would assume that vacuum sealed would prove to extend the shelf life of the product considerably as it does with all other foods herbs. Like Hydrodawg said, you can't just stick them in a mason jar and tighten the lid though. Although it's pretty tight, there is still amount of air leakage from that and thus oxidation and degradation of the THC will still be occurring. I like to leave my stuff in jars for 6 months max, then it gets vacuum sealed.