It’s likely that your Kindle’s battery will last as long as you own the Kindle, unless you happen to be one of those frugal types who hangs on to a device for a lot longer than the average consumer. But if your battery does go kaput (edit: and you don’t have any warranty protection), you can change it out yourself with a little patience and some careful prying open of the Kindle case.
Here’s a video tutorial from NewPower99.com, a website that sells replacement batteries for a wide variety of devices. I have no knowledge of this company and can’t vouch for them; I’m simply sharing their tutorial video because I think you’ll find it useful.
Also, I’m not sure why they chose Bolero as the music–I think Flight of the Bumblebee would be far more exciting (and funnier) when you’re tearing into an expensive electronic device.
Remember, opening the Kindle will void your warranty if it’s still in effect–but then if you’re still under warranty, you should probably just contact Amazon for help in the first place.