You might also want to check your model Converter/Charger you are using. Your age of RV Trailer might have the single mode type converter/charger unit installed that puts out a constant 13.6VDC all the time. This charge voltage is right on the edge of boiling out battery fluids over time.
If you have the single mode type converter/charger it might be a good idea to change it out for a multi-mode SMART MODE converter/charger unit. The PD4600 or PD9200 series converter/chargers are great SMART MODE units to have.
These smart mode units will take real good care of your batteries for you.
Roy Ken