Is it possible to put batteries in parallel to increase battery life?

I was just wondering if it is possible to put batteries in parallel to increase battery life? I was thinking of the Go Pro Hero 3 camera.

I know they have a battery backpack, but I just wanted to know if it was possible to stretch the battery life, if you bought lots of batteries and put them in parallel.... And attach the pack of batteries with a cord.

Or is there another way to do the same thing?