Many ways to fix; not all will work.
After getting their brand new iPhone 4S, many people were dismayed at the abysmal battery life they were getting out of it. People reporting anywhere between 4 to 8 hours of actual usage, before the battery flats out completely. There is a 134 page thread as of writing this article on the official Apple forums with people trying to figure out how they can improve battery life.
One of the issues pointed out by The Guardian is that there’s a location service bug introduced in the GM release of iOS5 that could be causing this. Apparently “Setting the Timezone” seems to be the main culprit (found in Settings -> Location Services -> scroll to bottom to “System Services” -> Setting Time Zone.) What appears to be happening is that a bug keeps the location services always on when ‘Setting Time Zone’ is is turned on, resulting in your iPhone 4S constantly trying to triangulate its position via cellular antennas and GPS tracking. Turning this setting to off seems to have helped a lot of people, but not everyone.
Many people have also suggesting a complete factory reset of the iPhone 4S and then not restoring the data from the PC (resulting in a completely new phone, so to speak) but to download all of your synced data from iCloud. Others have suggested that turning off Calendar notifications also helps. Among these three, you should be able to get your iPhone 4S’ battery life back to normal, but if you have any other suggestions that work, do share.