The following websites have some good suggestions for preserving your battery life on these devices and making them last longer :)
Tricks to Keep Your Device’s Battery Going and Going
Top 15 ways to extend the life of your laptop Battery
A more technical explanation of preserving the battery life of lithium based batteries
New technology with batteries is coming
A little background on battery types from the NYT article:
The older generation of nickel cadmium batteries suffered from memory issues; if you didn’t fully charge and discharge one, it would hold a progressively smaller amount of juice.
Today’s lithium-ion batteries don’t suffer from memory loss, so it is safe to top off a battery.
Lithium-ion batteries cannot be overcharged; a device’s circuitry cuts off the power when they are full. However, manufacturers still recommend that a laptop not be continually connected to power once the battery is at its capacity. If a laptop won’t be used for several months, it should be stored with the battery in a 50 percent charge state.
All batteries can be fully charged and discharged for a fixed number of cycles; lithium ion batteries typically last between 300 and 500 cycles. Information on the number of cycles can be obtained at manufacturers’ Web sites, or at batteryuniversity.com.
No matter how well you husband your battery’s resources, there comes a time when you’ll need to send your battery to its final resting place.
Like most things nearing the end of their life, your battery will stay awake less and sleep more. “If your battery lasts only an hour after you’ve charged it,” said Anthony Magnabosco, owner of Milliamp.com, a battery replacement company, “you know its time is up.”
The following are 5 ways to lengthen the battery life on your laptop from the article :"top 15 ways to extend the life of your laptop Battery":
1. Defrag regularly - The faster your hard drive does its work – less demand you are going to put on the hard drive and your battery. Make your hard drive as efficient as possible by defragging it regularly. (but not while it’s on battery of course!) Mac OSX is better built to handle fragmentation so it may not be very applicable for Apple systems.
2. Dim your screen – Most laptops come with the ability to dim your laptop screen. Some even come with ways to modify CPU and cooling performance. Cut them down to the lowest level you can tolerate to squeeze out some extra battery juice.
3. Cut down on programs running in the background. Itunes, Desktop Search, etc. All these add to the CPU load and cut down battery life. Shut down everything that isn’t crucial when you’re on battery.
4. Cut down external devices – USB devices (including your mouse) & WiFi drain down your laptop battery. Remove or shut them down when not in use. It goes without saying that charging other devices (like your iPod) with your laptop when on battery is a surefire way of quickly wiping out the charge on your laptop battery.
5. Add more RAM - This will allow you to process more with the memory your laptop has, rather than relying on virtual memory. Virtual memory results in hard drive use, and is much less power efficient. Note that adding more RAM will consume more energy, so this is most applicable if you do need to run memory intensive programs which actually require heavy usage of virtual memory.