This might interest PowerBook / iBook / cell phone users. According to a paper on batteryuniversity.com,
[..] a lithium-ion battery provides 300 to 500 discharge/charge cycles. The battery prefers a partial rather than a full discharge. Frequent full discharges should be avoided when possible. Instead, charge the battery more often or use a larger battery.Lithium-based batteries have a lifetime of two to three years, and the speed at which the they age is function of temperature and state-of-charge.
If possible, store the battery in a cool place at about a 40% state-of-charge. This reserve charge is needed to keep the battery and its protection circuit operational during prolonged storage. The most harmful combination is full charge at high temperature.The bottom line is to avoid full discharges, recharge more often. Keep the Lithium-ion battery cool but do not freeze. Avoid a hot car.