Extending the Life of a Laptop Battery

I am trying to research how to get the most life out of a Laptop battery. My wife has a Dell Studio 15 with a 9 cell battery. She is using the laptop 90% of the time on A/C Power. I thought about taking the battery out to try and extend the life of it, but am not sure this is the right thing to do. Can some people give me some tips on what to do. How many years should a battery last and does that depend on how much your using it by battery. Thanks

Best life- 40% charge, store at room temp out of the lappy.

Thanks for the tip. I have read other people's advice and this 40% charge and store has come up a bit. I thought the following article had some good tips.

http://www.time4tech.com/article18a.html