Apple's advice on storing your device to maximize battery life

From Apple's Maximizing Battery Life and Lifespan page: If you want to store your device long term, two key factors will affect the overall health of your battery: the environmental temperature and the percentage of charge on the battery when it's powered down for storage. Therefore, we recommend the following: Do not fully charge or fully discharge your device's battery -- charge it to around 50%. If you store a device when its battery is fully discharged, the battery could fall into a deep dis...