You can maintain your batteries with 40-60 amp solar charger and controller.
Your big advantage I see you live in sunny Calif.
1st you have to start with fully charged batteries, then use a disconnect switch to isolate your batteries from any parasitic draw.
You will do fine.
I maintain my 5 batteries, 3 house and 2 starting batteries this way, with 50 W solar when in storage.
M SIL and daughter do their TT with just one single battery with a 15 W solar with built in controller they flop on top the roof of their tt and do fine. they also have a battery disconnect switch direct on the battery to eliminate any draw. We are in So. Calif.