I guess we are fortunate that our off-road POPUP fridge runs on 12VDC -120VAC-gas
We always start out with a cold fridge with minimal cold supplies in it. We will fire up the fridge on 12VDC when we are around 2 hours out from the planned camp site on a quick one day drive trip. If driving for a couple of days we will run the fridge on 12VDC more during the trip. Usually don't have problems with it getting warm in it. We also don't stock it up heavy with cold items until we arrive at the camp site. Usually pull into a WALMART and get our cold things for a couple of days supply just before pulling into the camp site.
Since we have been running the fridge and having a few cold things in already it doesn't have to take along time to get up to speed on keeping added things cold.
We also have room either on the trailer deck or in the back of the truck for our 5-day freezer chest. It is always filled up with ICE on the trip and have a plastic container sitting on top of the ice to keep things nice and cold and not water logged. The 5-day freezer chest of course is our PLAN B item...
Roy Ken