"If it ain't broke, don't fix it"
The life of the battery will depend on how you use the laptop (or any PC). If the unit sits unused and unplugged for day or weeks at a time (the battery removed from a laptop would be equivalent) then the 3v battery will run down much faster than a PC that is always plugged in and/or the laptop battery is always in and charged.
I have 10 year old PCs here with the original batteries and they are still reading 3v+.
Many laptops use the same 3v battery that desktop motherboards do, but some use a proprietary design. If you can find a "Service Manual" online for your laptop you could find out quickly which you have.
But here is the fast test for your laptop:
- Shut it down.
- Remove the laptop battery.
- Let it sit overnight.
- Put the battery back in, turn it on and go into the BIOS settings. If the time is still correct the 3v battery is working. If not, then it is time to replace it.