Basics that people can probably agree on:
1. You need to have enough capacity to serve your power needs without discharging your battery more than 50% (regularly). It would be convenient to have instrumentation to know how much current you are using and how much you are charging so that you can have an idea about current State of Charge
2. Carrying along a source of charging power (solar panels, genset, plugging in for an opportunity charge when available, charging from vehicle power while moving) will allow you to have less house-battery capacity (minimize weight/space/cost to what you actually use/need).
3. Reducing your consumption will extend what battery capacity you have: replacing incandescent bulbs with LED's, using propane
on 3-way refer's, shutting off fans that can run continuously unattended (like my furnace
when it runs out of propane), and other loads unneeded/unknown.
There is no such thing as a free lunch. There are good deals, and poor deals, separated by what we think is important in power storage and delivery.
IMHO, the very best deal is plugging in to the 12 cents per KW/H grid. Small gensets (1000-2000 Watts, light
enough for the weakest adult to stow) running on gasoline are very powerful battery extenders when coupled with the right charger. Solar
panels that can put out a charging current of 10% of your battery capacity are a worthy investment in not running the generator
when your batteries are 85% full. In the spring, in areas that have lots of golf courses and people using golf carts, you will find good deals on 6v golf cart (or golf "car") batteries at CostCo/Sam's Club/etc. These batteries are designed for abuse and neglect and will serve you well when babied in RV house-battery service.