I've found that the batteries in handhelds are one of the first things to go out. With Palm handhelds, it can be costly or difficult to replace batteries. I have many Palm m515s in a cabinet at school that no longer hold a charge. Right now it doesn't seem worth it to seek battery replacement. Fortunately, my iPAQ 5400 has a removable battery so when it gave out (from being left on the charger for months on end), I found an inexpensive replacement on eBay. Unfortunately, now I have an iPod mini in need of a new battery. I can find a battery cheap on the web, but it doesn't look at all easy to actually change.
It's important to care for your electronics' batteries to have them last as long as possible so you won't have to replace a battery so soon. There's an abundance of information about caring for your handheld's battery. The Lithium-ion (a.k.a. Li-ion) batteries found in handhelds, cell phones, notebook computers, and digital music players don't require much maintenance, but there are some tips online to help you extend the life of Li-ion batteries.
palmInsider posts About Batteries. There are six basic ideas offered for getting the most out of your Li-ion batteries. These ideas include reading the user's manual, fully charging your first time, never fully draining the battery, and not leaving the handheld charging all of the time.
BatteryUniversity.com has a Do and Don't Battery Table. The column for Li-ion batteries encourages frequent charging, storing at 40% charge in a cool place, and avoiding full discharge. The How-To Prolong Lithuium-Based Batteries page suggests calibrating the fuel gauge once every 30 charges by letting the battery become very low. It's an often occurrence for a handheld's battery meter to be inaccurate. The palmInsider article says to warm reset your handheld (i.e. poke a Palm handheld's reset hole while holding down the Up button) while it is on the charger and leave it charging overnight to recalibrate a Palm handheld's battery meter.
Apple uses Li-ion batteries in its notebooks and iPods. This page gives some more insight into these batteries. It says that Li-ion batteries need to be exercised for maximum performance. Apple suggests that if you don't use your device often, at least complete a charging cycle once a month to keep the battery's electrons moving. Additionally, excess heat can cause batteries to lose capacity. If you charge an iPod or handheld in a case, be sure the case is not making the device warm. If it is, charge without the case.
You may be wondering why handhelds and other electronic devices don't simply use good old AA Alkaline batteries. Apple's page puts it into perspective: "if your iPod were powered by 4-AA Alkaline batteries and you used one pack per week (which is conservative), after two years you would have spent over $200 (buying in bulk) and piled up 400 dead batteries for your local recycling center."