Extending battery life can be achieved by limiting screen brightness. Ubuntu 13.10 (Saucy Salamander) by default sets screen brightness to 100%. I have found that 50% screen brightness is more than adequate for indoor viewing. Saucy currently doesn't save your screen brightness settings when you log out or shut down. Through some web searches, I discovered "xbacklight". It's a command-line utility to set your screen brightness. You install it, add it to your startup programs and set the screen brightness to a default level of your choosing.
xbacklight is available through Ubuntu Software Center or via the terminal ("sudo apt-get install xbacklight").
Search (super-key) for "Startup".
Click on "Startup Applications".
Click the "Add" button.
Command: xbacklight -set XX (Where "XX" is the numerical percentage of screen brightness)
Here is a screen-shot:
Save your new Startup Application and restart to test your new default screen brightness!