Apple has posted various recommendations on its Web site for how to treat the iPod battery to ensure a long life:
Don't expose the iPod to extreme hot or cold temperature ranges. (In other words, don't leave it in a hot, parked car, and don't expect it to operate on Mt. Everest.)
Use the iPod regularly (not that you wouldn't). And be sure to charge it at least once a month to keep that battery chemistry peppy.
Put the iPod to sleep to conserve battery power. (Press the Play/Pause button until the iPod display goes blank and the iPod settles into slumber; on the Touch, click the Sleep/Wake button on top.)
Take the iPod out of any heat-trapping cases before you charge it up.
Use the Hold switch when you're not actively fiddling with the iPod's controls. This keeps it from getting bumped on automatically.
When you see the Low Battery icon or message, plug the iPod into the computer or an electrical outlet with the AC adapter. The iPod battery indicator shows roughly how much charge is left in the battery.
Features like the backlight and the equalizer—or jumping around your library—can make the battery drain faster, as can using big uncompressed file formats like AIFF.
That wireless chip inside the iPod Touch is sapping power even if you're not trawling the Web. Save energy by turning it off when you don't need it at Settings→Wi-Fi.