Thor Palazzo 33.3 diesel
Brand: Thor Motor Coach
Model: Palazzo 33.3 34'bunkhouse
Interesting question, and one that we all have different experiences with -
though, there's no 'standard' amount of 'time' that your four 6v batteries, at 'full charge', will power the Fridge and several lights.
First - the fridge is not just a constant draw. It is ON when it needs to bring the temp down. And the light comes ON when you open the door, of course. Your TEMP setting will impact this power consumption and run time, the number of times you open the door during that time, AND the temperature and weight/number of items you are cooling.
Second - the batteries are being used by more than just the fridge, of course, and any lights in use will impact the usable 'hours' for your batteries. Remember, also, that 'silent' items that draw power are sometimes easily overlooked, such as device chargers, TVs, even when not used, the Inverter itself, fans, and anything else that might be plugged into an outlet out-of-sight, or mind!
Third - the batteries themselves have a certain lifespan(number of charges, discharge cycles, etc) and the age of yours will weigh in on hours of usable power.
Note: the usable hours of Fridge power, and any items powered through the Inverter, also can be controlled, or limited, by you to also preserve battery levels through the night - the LBCO(LowBatteryCutOff) setting on your Magnum Inverter display allows you to tell the Inverter when to 'ShutDown' when the batteries reach a critically low level, such as 11.5 or 10.9, whatever Voltage level that you don't want it to go below. This preserves the ability for your batteries to retain enough power for you, or the AGS, to crank the Generator later, or in the morning, etc.
(this does not apply, though, to strictly 12v items, such as lights, fans, 12v TVs, etc., as they run directly from the batteries)
Some suggestions to get through your situation might be that even if your Fridge were to be turned OFF during the overnight hours, you'd still be ok in the morning, OR for the last several hours of generator usage, run the TEMP setting on the fridge to as low as possible to get it as cold as possible before the overnight hours : )
Some of us may get 12 hours of Fridge power from the batteries with no problem, others may only get 5, etc... it's not an exact game, as in any electrical usage scenario, it all depends on so many variables - even the outside and inside temperature of your coach is going to impact it.
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
100,000+mi since '14 - US, Alaska, Canada - Northwest, GA! (also, '14 Gulfstream Amerilite and '07 ForestRiver Rockwood) : )