You bought this new or used? I'm not sure what the standard duration of the battery is but if it's used it could be less than what it used to be. I'm assuming you have the 6-cell version of your battery. They sell a 12-cell version as well. A quick google of your model # came with this as an example:
http://www.battery4us.com/toshiba-no...655D-S5159.htm
As you can see slightly more expensive but also much bigger and heavier. Look around ebay or google shopping for best deals on the battery. Maybe someone might know a good site to buy batteries from ?_?
Also to conserve battery life try to run if possible less utilities wifi, card reader, usb devices etc. Low back-lightning helps a ton. Set power options to turn off screen w/e not in use etc.