The question of how much opening the frig door, and for how long, has come up a couple of places lately, and with the low cooling power of the absorption frigs, and battery power used be the compressor frigs, it is a real issue for RVers to think about, IMO. I am not going to get into theory, or my opinions, as that has been done, as it has with others. Here is test and evaluation study done by a major university in the Engineering department, and it is one of the better that I have seen. Most of the useful information is in the first few pages, with the details of the testing and calcs further in. Make your own conclusions.