Anybody gang together two 6v golf cart batteries for their house bank? GC batteries are quite robust and by wiring them in series you can get 12 volts and a whole bunch of amp hours. The biggest advantages are space and weight. When you get old like me, it's a whole lot easier to lift a 6v GC battery than trying to hump a 4D.
The house bank on my trawler is 4-6v AGMs. We run a 2000w inverter, watch TV all night, cook with a microwave and toaster oven and make coffee with a Mr. Coffee every morning. When we travel N & S in the Spring or Fall we travel most days. I monitor our battery condition and we seldom run our batteries below 65%. The batteries are recharged by the 120 amp engine alternator as we travel and we almost never run our generator.