The solar turns off each and every night. I believe you are overthinking this.
If you have enough solar wattage then you don't need the wfco to be replaced.
What solar controller do you have? Solar charge controllers tend to be much more sophisticated than converters.
My solar controller has a temperature probe on the battery bank. When I had flooded jars it was rare for me to need to add distilled water. But checking them laying down in the snow was not much fun.
The solar controller allowed me to garner 9 years of service from Walmart Marine batteries. When they did fail I replaced them with used telecom surplus acid AGM units. (no more laying in the snow).
If you plan on a good inverter, many of those have a temperature probe as well. I've seen my charge voltage hit 15.4 (I limit it to no higher than that).
