It depends on your converter and your climate.
If you have the notorious WFCO converter that doesn't like to change modes and are in a hot climate, you will likely fry the batteries.I am in Phoenix, and that was my experience. My WFCO was stucck at 13.6, and that was too high here. I changed the converter to a Boondocker, and it worked fine. Some people in cooler climates have reported that the WFCO works fine for them.
FWIW, I have a collectible car in my garage that rarely gets driven.I have a battery tender brand charger on it. That works fine. That battery lasts more than 10 years. The cheaper tenders do not work as well.
