I've find a few nice resources with plenty of explanation in the Internet but nobody said his/her suggestion was the true thing. So I decided to try a few strategies myself out.
Here's my story and make your own conclusions out of it:
I bought a Dell Inspiron 1520 back in 2008 September. It has a 9-cell battery Lithium-Ion.
It was said to be possible to work for 3 hours with normal usage on "power management settings" and I have tried it and it proved to be true. And I wanted to keep it this way for as long as possible.
I mainly use my laptop as a "desktop laptop" and it's constantly plugged to the AC adapter.
- The idea was to discharge the battery to 30-50% and put it in a cold place (refrigerator) - this way it is supposed to be best preserved for a long time.
The next idea proved to be more successful. I've put reminders every 2 weeks to use my laptop on battery only and drop it just under 50% of charge. This is somewhat of an exercise for the battery and it doesn't "forget" how to charge/decharge.
- I put 2 week reminders in Google Calendar to use laptop on battery only till 50% battery capacity.
I have used this technique for the last 24 months. I'm using these days the laptop more on battery only and it survives more than 2:30 hours. That is with slightly dimmed screen and power settings ON, Windows 7 and wireless put on. I'm using it as if it's on AC power.
So I think this little technique has helped me.
Comparison with a friend of mine using a Sony laptop only on AC power and now he says it manages to keep it on battery for about an hour. What a difference!
Piece of advice:
This strategy helped me, but can be harmful for your laptop and/or battery ! Do this on your own risk!
(I'm obliged to write this... )