Hmm, I use the exact opposite of your technique. I never drain the battery fully, and very often leave it plugged in for weeks at a time. I have had this battery in my iBook for about 2 and a half years now. I still get a solid 3
-3.5 hours of battery life surfing the web and using AIM (among other applications on and off). When the battery was new, I would get about 4 hours, but only losing about half an hour in this time is pretty good.

Maybe I got lucky, but I think the key to extended battery life with this type of battery is not letting it drain all the way.

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Giantmike's Website - http://homepage.mac.com/giantmike

Apple actually has a site about batteries in their devices:
http://www.apple.com/batteries/

There's a page specifically for notebooks too:
http://www.apple.com/batteries/notebooks.html

They say that you should "keep the juices flowing" by not leaving it plugged in all the time, and giving it times to discharge and charge. They also say you should let it discharge and charge back up again once a month. But if you've had good results with your ibook, then I guess I can't really argue with results. Maybe you are lucky ;). Or maybe your battery will drain in the future. But who knows :)