If you take it out of the freezer and open it immediately, it will still be cold and that causes condensation. You know? The drops of water on the inside of a refridgerator? And that water is not good for your acid. That is the reason.
As for your initial question, it is impossible to say. In some conditions that include ambient temperatures acid seems to stay well for one or several years. In other situations something curiously went wrong and it could be any number of the factors: UV radiation (part of normal (sub)light), temperature, water (also the water in the air), and oxygen. The conspire together to destroy LSD.
Just to be sure put it in the fridge or freezer if you do not trip often, but find a dessicant to put beside it and put all of that inside a completely airtight container! It must really be closed off from the air. Otherwise: freezing condensation!
For other questions visit the LSD Storage Thread and continue there, you can find it through either the FAQ or the Index, there is event this particular question covered in the FAQ I made so I am not too keen on keeping open yet another thread. Thanks.
Links are in my signature, here below on the right. USE EM please
