I do not have a convertor. My usage is minimal with lots of low current draw items that have replaced power hungry incandescants etc.
I have a small trickle charger on the batterry. It does not stay plugged in for any length of time, only long enough to get my frudge cold on AC when I am prepping for a trip, or when I have shore power at a site, the 12v items run straight from the battery, so it is continually tapping power off the battery.. while the battery charges.
I have solar
for other times, and a charge controller helps keep the battery charge regulated.
When in route, I charge from my Element.
This arrangement works for my minimal needs and I have no fear of ruining my battery.
Even living in an area that gets very cold in winter, often iced in, I have not had a great need to run a heater to keep stuff warm in the trailer when not in use.
My heater is a cat heater with no fan, so it uses no electric power. When I have AC available, I run a cube heater.
Your needs may vary... I like to keep it simple. I have seen so many convertor horror stories here. To ME, it seems yet another item to cause problems. I haven't missed not having one. I have never had one, as a matter of fact.