Umpqua,
I believe you have a Parallax 7300 series converter/charger in your camper, which is a single stage charge controller, hence the reason you are burning up your batteries by leaving it plugged in all the time. I replaced my Parallax 7300 series with a nice 3-stage charger/converter from
Bestconverter Magnetek/Parallax-6300,7300 Upgrade KitI replaced mine within a month of owning the camper and I bought it new. I leave mine plugged in all the time and have the same set of batteries (7 years now)and I have had no problems. A friend of mine upgraded his 2006 Bigfoot 2500 camper with the same charger/converter after he saw mine. Its a pretty easy project with the directions that are on Bestconverter website.
Good Luck