How long is a life span of laptop battery?

I would like to ask how long the laptop battery lasts before a replacement under 2~3 hours normal use. I read 12~16 months somewhere. Is this about the right life span? I think if you have to replace your battery that often with the price range of $200 ~$300 a little bit expensive.... The battery of my Laptop... show more I would like to ask how long the laptop battery lasts before a replacement under 2~3 hours normal use.

I read 12~16 months somewhere. Is this about the right life span? I think if you have to replace your battery that often with the price range of $200 ~$300 a little bit expensive....
The battery of my Laptop Vaio, VGN-FE570G is now almost giving up after 16 months. After the full charge, it only lasts 10 minutes, which used to be at least 90 minutes. I know I have to buy an another one, but I just wonder I have to do so for every 16 months? Or extended battery life span is longer than the standard one? I also own Vaio VGN-UX 280P. Is the battery life almost the same?

I will be very appreciated for your answer.
Thank you.
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