I have a 2013 378ts, and when stored in my pole barn I have the unit plugged in and I leave the battery disconnect in the on position. The batteries are maintenance free and I never have a battery problem. I guess I am not sure why people disconnect the battery switch when the unit is plugged in during storage. Since 2001 I have had 3 5th wheels and now the Georgetown and never have had a battery problem. It doesn't take a very big battery draw to kill a battery in a short period of time, and since you already have a built in battery charger why not use it and keep the batteries charged. Letting batteries go dead is very hard on the battery life and will cause premature battery failure. Even plugged into a standard 110 volt outlet, the charger will keep the batteries charged.
Mickey & Sue Stamper
2013 GT XL 378TS
2013 Ford Escape on Landgrebe tow dolly