I always heard that a full fridge cools down faster than an empty fridge. Something about having objects that capture/absorb the cold.
Currently I leave fridge on...it has some water, condiments, etc... stored in it.
When I was NOT leaving it on...I would place several ice packs (or frozen food items we wanted to thaw) on the shelves. Fill the door shelves with bottles of water, beer, etc... I cooled down on electric, because propane was/is expensive, and I never notice the raise in the household electric bill due to the trailer being plugged in. Typicallly, it would be down to the desired temp within 24 hrs.