I am sorry that happened to your tea. You must feel very bad about this since it seems to me that you love Longjing quite seriously. I cannot comment on what really happened to your Hangzhou batch; many things could have. As for ours, we simply follow strict procedures in storage and handling as I have explained in this article:
We do have some very special batches stored at below 0°C, but Longjing from 2012 has been stored only as usual at around 5.
Before storage, however, proper processing and drying provide the fundamental material basis. Packaging materials and proper sealing are critical as well.
