It would seem that battery care is a bit of a black science.
What you need is a way to charge your battery between trips. What i use is a Solar powered Battery Minder desulfator charging system.
What I love about this system is that it will bring most old borderline batteries back to life by removing the sulfation on the plates. It will also make good batteries last 7 years or more. For your needs you would need a larger one. http://batteryminders.com/details.php?prod=SCC-180
This one needs you to supply the solar panels, but for set up at a remote camp would take care of several batteries, and help make them last. one thing for sure. Running 12 volt batteries all the way down will destroy them quick. The best thing is to keep them charged as much as possible. One note about the battery minders, they will charge a battery to its maximum capacity without boiling out the water. From my experience they do work. Good luck and great camping.
BBuchorn