Ron, your battery will drain even if the disconnect switch is turned off through parasitic draws like the CO2 detector, propane detector, and even the radio. The only way to truly shut off everything is to disconnect the battery or install a disconnect to the negative battery cable.
As for charging batteries on shore power, your battery disconnect switch must be on for the converter to do its job and keep the batteries fully charged. You will need to check the water level in the batteries at least once a month and top off with distilled water. Good luck and safe travels!