I'm in the "as many batteries as you can fit or afford ... whichever comes first" camp.
As such, all we can fit are a couple of 12V Group 31 AGM batteries. We can go about three (3) days on these before recharge ... keeping our propane/12V refrigerator of course on 24/7, using two non-heated CPAP machines during the nights, and keeping the furnace set to 65 degrees during the nights.
We can recharge three different non-solar ways: The main engine alternator, the built-in 4KW generator and the converter, or a 650 watt portable generator and the converter. These recharging methods work well because AGM batteries charge faster than liquid acid battereis - but they do cost more to buy initially.