The colder a substance, the slower its molecules "Move" - all substances are in a state of molecular motion, even solids... Liquids having more kinetic potential, and gasses the most. The idea here is that the colder you keep your LSD, the slower the molecules move, and the less likely they are to "decompose". So bottom line, my acid is in my freezer.
Acid is also very photosensitive, so keeping it out of the light is very important as UV rays (As Phreex said) also cause our fagile LSD molecules to degrade at a faster rate, this is why my acid is also in a dark vial, wrapped in aluminium foil, in a metal altoids box.
I say take ever measure you can to preserve the strength of what you have... nobody likes bunk acid!
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"I dislike the drug you are using, but I would defend with my life your right to use it."
- Paraphrase on Voltaire
"He who makes a beast of himself gets rid of the pain of being a man."
- Dr. Johnson
"We do not sense imagination enough to sense what we are missing."
-Jean Toomer