How long to get cold!

Hi! Hope some of you can help. I have just completed an overnight for the first time in my new TT it was great! Just have a question on the refrigerator though. I have a Dometic ref. it seems to work but how long should it take to get cold! I have a ref that works only on AC for the outside kitchen and that got cold real fast, but that is a standard dorm type frig. I understand that the one in the Trailer is a evaporator type and takes longer, but what is longer? Please help as I am sure you all have been here before, Thanks