Assuming a 220 AH rating for each battery, your total capacity would be 880 AH. The fridge draws 1.5 KWH/day, on average. That is 125 AH/day at 12v. With a target of 50% state of charge until recharging the batteries, you should be able to run the fridge 3 1/2 days. You will not want to wait until the batteries are at 11v because this will quickly ruin all your batteries.
The above math is not exact because you will also have the result of the Peukert effect on the constant draw from the batteries and the inverter loss so that 3 1/2 days may be down to 3 days in real-world use.
