If your trailer has the smart mode type converter/charger on board this will keep your batteries in pretty good shape and not boil out your fluids.
The older single mode converter/chargers that always put out 13.6VDC when plugged into shore power is right at the point of boiling out your battery fluids. When I had one of those type of converter/charger units I checked my battery fluids at least every two weeks.
Letting the Battery fluids get below the tops of the internal cores will shorten your battery life big time.
Most trailer manf after 2012 usually have the smart mode converter/charger units installed. Post the model numbers...
Roy Ken