According to some, Wifco converters have a reputation (personally unverified) for keeping too much voltage on the battery when the battery is fully charged. This will cause loss of water from the battery cells over an extended period.
If left plugged in, I would check the level in the cells periodically until you know what is happening.
I installed a cut-off switch my a-frame (I have 2 golf cart 6V batteries for 4 days of dry camping). I leave the camper plugged in for a few days after a trip to fully charge. I then disconnect the batteries with the switch, and leave idle for up to 2 months. Then I will plug back in again for a couple of days. Hopefully, we go camping again before 2 months are up!
A fully charged battery will not be harmed by freezing temps.
2104 Rockwood A122