Avoid frequent full discharges: Several partial discharges with frequent recharges are better for lithium-ion than one deep one. Avoid frequent full discharges because this puts additional strain on the battery.
Calibration is important: Batteries with fuel gauge (laptops) should be calibrated by applying a deliberate full discharge once every 30 charges. If ignored, the fuel gauge will become increasingly less accurate and in some cases cut off the device prematurely.
For prolonged storage: Keep the lithium-ion battery cool. Avoid a hot car. For prolonged storage, keep the battery at a 40% charge level. Consider removing the battery from a laptop when running on fixed power.
Keep it cool: If you have a spare lithium-ion battery, use one to the fullest and keep the other cool by placing it in the refrigerator.
Check manufacturing date: Avoid purchasing spare lithium-ion batteries for later use. Observe manufacturing dates. Do not buy old stock, even if sold at clearance prices.