No matter what, if the floating voltage (after batts are fully charged) is over 13.4, DON"T leave it plugged in in warm weather. In the colder temps batts can handle highter voltages, 13.6 - 14
I know that w/ my PD9245c converter plugged in all the time, float voltage is always between 13.1 and 13.3, depending on temperature. And my batteries use very little water, once, possibly twice a year, but nothing like a 1/2 gallon.
I also installed a digital voltmeter right by the entry door, every RV should have one !