Possible Duplicate:
Is it better to use laptop on battery or on AC power?
When laptop battery is fully charged, what is the best for battery life : use the battery or to use AC adapter (in general) and why ?
Possible Duplicate:
Is it better to use laptop on battery or on AC power?
When laptop battery is fully charged, what is the best for battery life : use the battery or to use AC adapter (in general) and why ?
Battery life is based on charge cycles (number of times charged/discharged) and temperature. If you've got an outlet and your battery is charged (or mostly-charged), remove the battery.
If you are using an AC adapter all the time, the battery isn't charged or discharged at all, and because of that it's resource is not depleted. Battery's life only decreases when current flows through it, or, in the other words, if you charge or discharge it.
In my opinion:
If you can plug to AC, just do it and plug out your battery.
And just like any cellphone, if you start discharging your batteries go to the end of their power, in this way their live will be longer.
Batteries should be for where no grid is available.
In my opinion. ;)