c370... golf cart batteries are excellent as house/inverter banks. dont' know where you get the idea that they don't last, maybe of you use the wrong charger and neglect them, otherwise they last. I use 4 8v GC bat. for main banks (2) and the last set lasted 4 to5 years (pretty good in So FL)
2 pairs of 6v batteries will give a 440 amp/hr bank, that's much more than you can get out of standard batteries.
the original post mention installing batteries near bilge pumps... that means low in the bilge which i dont' think is ideal. i addtion to be secured, batteries need terminal covers to eliminate the risk of accidental shorts.
Jimmy, the Freedom series inverters work completely automatically, they dont' care whether AC is coming in from shore or genny. they automatically switch to inverter when A/C is disconnected and switch back to charge mode when it comes back in. the echo charge is only used to keep another bank charged but it only charge when you're charging the main bank.
JA... depedning on your fridge/freezer size, 400 amp/hr shoudl get you thru the night and into themorning, also depending on what else you are using. i have an 800 AH bank for my freedom 30 and get just about 24 hours for the full size fridge/freezer, a few lights, coffee maker, etc...