Here's Hyperion'a advice on lipo storage - good for any brand lipo -

"Storage - Lipo should never be stored fully charged, or with less than 50% of capacity remaining. We strongly recommend Hyperion EOS chargers, as they have automatic STORE functions to insure that the packs are in the range of about 60%~70% capacity (3.78V~3.92V resting voltage per cell). After returning home for the day, simply use STORE MODE to achieve this automatically. Batteries are best stored in a cool, dry environment (2~20 °C or 37~68 °F)."


Most recommend storing at 3.85v/cell simply cause its in the middle of the above range. Note this is the resting voltage.