personally i would stick with a Toshiba replacment available in both 6 and 12 cell... i have a L650 so this may not be the exact one that you are after...
http://www.mytoshiba.com.au/products...sories#details
reading the reviews on the
US site it looks like the 12 cell will run your lappy somewhere between 5 - 7 hours... hmmm now you have me thinking about it...
cheers...
Ian...