It’s a good thing to occasionally review how to take care of your things. This is from http://www.ipodbatteryfaq.com/
Lithium ion batteries are good for 300-500 charge/discharge cycles. A “charge/discharge” cycle generally consists of an extended charging period, and an extended discharging period. A quick charge, listening for 30 minutes, and charging again, for example, does not constitute a full “charge/discharge cycle”, but could rather be considered a portion of one.
Also, many, many factors affect how much you get out of each charge, as well as how long the battery will last overall. The main factors include charging patterns, the routine amount of discharge (i.e., Do you use it until it dies? Use it for an hour or two and recharge?), temperature, storage, usage frequency, etc. Lithium ion batteries do not take kindly to frequent full or complete discharges. When possible, the optimal usage pattern – for any lithium ion battery – is a partial discharge, followed by recharging. A partial discharge can be anything less than a full discharge. However, an occasional full discharge is desirable (e.g., once every 30 charges) to calibrate the battery. Lithium ion batteries do not significantly degrade, or develop “memory”, even if charged at irregular intervals; irregular charging is acceptable. An iPod can also safely be attached to external power for extended periods of time. (For extremely extended periods of time, such as months, the battery will essentially be the same as if it were in “storage”; lithium ion batteries do not store well for extended periods of time at full charge. However, there is no way around this under these circumstances.) When possible, always use the AC adapter (or vehicle adapter) for extended charging, not a FireWire cable attached to a computer.