Life of an "average" battery

I was wondering, how long does the average battery last before it dies? I mean, I'm planning to use my current notebook for at least 4 years, and it would really suck if had to replace it in like a year or so. Are there any special methods of taking care of your battery?

My notebook is primarily used for home, so it has 24/7 access to a power plug. But a question that has just bothered me is: Is it better to keep the AC power plugged in (even at full battery) or to only keep the AC plugged in when I'm charging the battery? Or should I just take the battery out entirely?

 

You know what, a few months ago they did a homepage article on this website about your very question let me see if i can find it again.

As far as your question goes, it is best to charge your battery to about 50% and then take it out of your laptop and store is a cool dry place if you plan on using your computer plug into the wall for multiple days on end.

 

it will last a long time; if you just plan to use it as a sort of a UPS; i think it will last a good 6-8years, might go as far as 12 years....

but do run it down to about 20% every month or so.

 

Read this before you click the link. Most laptop manufacturers will replace you current battery within 1 year of purchase if it can't hold 50% of what it was design for. If you heavily use the battery multiple times nearly everyday for the first year, you can make them replace your battery for free. But first check your warrentee and make sure 1 year since purchase has not gone by. Normally, batteries last 1.5-3 years. It's a little over 2 1/4 years since my laptop purchase and my battery carries about 33% of what it could at best.
I believe this is it. http://www.notebookreview.com/default.asp?newsID=4356

 

There is also this Battery Guide, I agree with crinzema guess on lifetime. You will also read "a couple" of years. But there are so many examples more in line with what wobble said. How you use makes a major impact on longevity.