Mulehawk; I was surprised to read a study about front opening vs top opening fridges. Like you, I thought the "cold air would escape" and the fridge would not be as efficient. Well, I forgot my college physics. The air isn't retaining the cold, the mass of the stuff inside is. Air has very little mass. The air has very little effect on the ability to keep the interior cold, dumping ALL the cold air for a minute and then closing the door will not warm the contents very much at all, and thus not enact the motor to re-refrigerate the interior. There isn't much efficiency difference between front and top opening mobile refrigerators, assuming the doors are opened and closed the same amount of time.
The "best" strategy to prolong cold temps to keep power cycles less frequent is to make sure you have a nearly full fridge, even if it's just water bottles. The initial cooling takes longer, but the warming time is proportionate. Cool while driving, and then the amount of ah needed from house batteries is lower while parked. You're not "storing" the cold in the air, you're storing it in the stuff inside.
However, I prefer a top load for a different reason: nothing will fall out when you open it after traveling on a bumpy road, and you can stack stuff inside better to make more use of the space.
2015 T250 MR cargo w/windows, 3.7, 3.73 Limited Slip. Purchased new 9/2016. Richmond, CA
Go Ducks! track&field 84-86 I am the wet blanket you need but are afraid to admit