Computer battery life

Someone mentioned changing a computer battery.

Does anyone know what the "typical" life of a computer battery is?

Is there a way of checking the strength of the battery while it is in the computer?

Thanks.

Staninfr

Does anyone know what the "typical" life of a computer battery is?

Is there a way of checking the strength of the battery while it is in the computer?

1. 2 or more years, I'm talking about the CMOS battery.

2. If you have a battery tester you can check the CMOS battery which is nothing more than a battery used in digital watches.