We've got a 22cf residential fridge, and we like to boondock. To keep our batteries fully charged, we used to have to run our generator about four hours a day. We ended up installing solar and increasing the size of our battery bank. Now, we rarely ever need our generator.
A typical OEM battery bank will usually get you through one night if you've got a res fridge, but if you're going to be boondocking for several days, people with res fridges either have to get used to listening to their generator droning away for hours on end, or invest in solar and more usable battery capacity.
Kev