I have no experience with 12V batteries on my trailer as when I got it the lone 12V battery had been absconded with.
Learning from some of the battery nerds on this forum....some more aggressive than others......I decided that 2 - 6V batteries was the best way to go.
I just came back from 6 days of boondocking.....the batteries did great......at the end I was down to 12.1V.
Granted....I don't have an inverter to power a toaster and coffee maker....nor do I watch TV.
Just regular day to day use...swapping out to LED lights will help, as well.