Until the propane runs out!! Propane fired generators are a bit propane hungry and whatever you have may have to be shared with the fridge (small user) (or use 120V from genny (1300-1400 watts), the water heater, (or again use 120V), the stove/oven. There is no free lunch!!
You will more likely be limited by the very low capacity of the black tank, (only 12 Gallons).