I was trying to figure out a way to use the camera to take a pic of itself with mirrors lol. But then I just got lazy and googled and found this:
I guess I just use the crap out of mine. I'm a noob and just have the stock rom, maybe I'll try mighty rom. If the difference is that big, maybe instead of 13 hours I get 20.
Again this may not be the solution if you already have access to recharge spots, or don't mind carrying spare batteries. It's 100 bucks and all the cool kids make fun of you for your bulky 1980's phone.
I personally would rather carry one heavy thing (phone with extended battery) than two light things (less bulky phone with spare battery in shirt pocket) but if I had to do it again, I would probably buy that 2000 mah andida and just keep it in the car. $10 > $100. Hell, I'd buy two.