I would make sure you don't have any servos binding. If you have one that is buzzing then that will chew a battery pretty quick. After that I would look into higher capacity packs, I just bought a 1650mah unit from radicalrc.com for $16. I am not sold on the idea that nimh batteries are any better than nicad for a reciever pack, but I'll have one of each now so I'll be able to figure out which one I like better.

I have an rc truck as well so I run a duratrax ice charger which has a nimh top off feature that I intend to use before heading to the field.

I like the idea of getting a 12vdc charger because it works off of the 12 lead acid battery you pack to the field for your starter.