A laptop battery duration or life time will not last forever but properly maintained it will last longer than the manufacture designed it for.
Did you know that a it has a life span? That is once you apply a charge to the battery it will fail after a certain length of time?
It is a electrical storage device that uses a chemical reaction to supply electrical current to your laptop.
The composition of the chemicals will give the battery it's characteristics of how much amperage at what voltage
it can supply over a given time before the chemical reaction is used up.
One thing that the current laptop batteries have to be able to do is discharge the electrical content then take a charge to do it all over again.
Each time it is discharged then charged it use up some of the chemicals that make the storage possible.
Another thing that these batteries do is build up a resistance to the charge, that is if not completely discharged before charging
it will only charge up so much. Over time doing this partial discharge and charging will build up 'memory' and the amount of actual charge
it will hold will decrease.
So what is the expectation for
your laptop battery duration? Unknown.
Different notebooks use different types, you can read a full article on
laptop batteries here.
A couple of tips about laptop batteries:
discharge a battery to the point where the laptop will shut down before charging. (Not always practical but if you can do a discharge before you connect the laptop to AC the next time the chance of building up memory in the battery is decreased).
If your laptop is used as a desktop instead of a true laptop then discharge the battery to it's lowest point then remove it and store it. (You have to remember it is discharged before you take off on your next trip!).
Newer laptop batteries have a charging / discharging circuit that limits the
charge or discharge rate, this limiting of the power flow increases the overall
life time of the battery. However this circuit also has a high failure rate, the
state of the art for the components that make up the controlling circuit have to
with stand higher heat that the battery produces so the failure rate is higher.
In the near future this problem should be over come but until then if your
battery fails to charge it isn't the actual battery but the charge / discharge
circuit. (I paid $109 for a 7 hour battery that died in a little over six
months... not happy with that!)
Troubleshoot, repair, maintain, upgrade & secure...
If your laptop battery duration will not hold a charge for more than a half hour use replace it!
A battery that gets hot when charging is dangerous, replace it before it destroys your power supply!