Newbie has questions about a BL setup

Here's the link to the batteries http://www.all-battery.com

What kind of run time do you think I would get with that setup. Also if I'm content with the speed but not the run time, couldnt u run 2 6 or 7 cell packs in parallel. I dont think you would be adding voltage but you should double your mah. So you would have 24 cells total but only get the voltage of 12, I think.