The worst thing for a laptop battery is using the spinning media drives DVD/CD/HardDrive.
Virtual Memory, adds to the battery chewing up hard drive motor power.
Moving parts chew a lot of power.
A review I just read online gives it a poor battery life rating, probably because its a beefy laptop.
Conclusion
The Asus F3sv is a phenomenal 15.4” notebook in all respects. While it is relatively heavy and has poor battery life, it's compromised portability is vastly outweighed by its feature set, performance, build quality and total polish.
http://www.notebookreview.com/default.asp?newsID=3794
It doesn't sound right for it to be that low.
Just dig out your warranty and then call them or hit the website, or the dealer you bought it from.