The first thing to consider would be the conditioning of the battery. More namely your charging habits. The worst thing you can do for your notebook battery is always keep it on the charger or charge it while it's only half full. This will diminish the life of the battery giving you less hours of operating time. The ideal way to charge your notebook battery would be to use it until it is completely dead and then charge it fully.

The second issue to consider would be your usage habits. Using multimedia such as movies and music will kill your battery a lot quicker. Especially doing operations that are CPU intensive. Playing games will diminish your power supply a lot quicker than say, browsing the internet.

There are also different settings that can help preserve your battery life. Windows has different functions for notebooks. For instance you can set your power usage depending on what you are doing. You can set your notebook to act like a desktop if you are near a power supply to get the full performance out of your system. On the other hand you can also set it to use power as efficiently as possible if you are on the move. These setting change things such as the amount of power the CPU uses, the brightness of the screen and so forth.

In the end it's up-to the individual user. Some notebooks come with the option of a second battery which can double the power your notebook has at your disposal but this is often costly. Also there are more advanced batteries that can be used but again they will cost you extra.