For what it is worth my fan was mounted vertically (horizontal air flow) at the top right side of the fins, siliconed to the top of the fridge and top of the fins (just a tad to keep in place really).  I considered the possibility that the lower temp induced by direct contact with the cooling fins was the cause of the short life, but I don't really know.  As I said this one ran approx 750 hours.  Another note.  A digital thermometer I mounted revealed daily high temps inside the fridge in the 55 range (even 60's at some points),  during the hotter days of August (IE 100 degrees).  the temp sensor was mounted to the center of the fridge ceiling, likely the warmest place in the unit.  Having said that I believe that the temperature of any particular food item probably never got nearly this warm (55) as they would be much slower to warm.  Even with the elevated daily temps (morning temps would regularly be in the 30's or 40's during a hot night) milk would keep (and "taste cold")  for 4-5 days no problem.  maybe more but it rarely lasted that long.  Nothing went bad the entire trip. (2 months).  One other thing!  My fridge was going out frequently during the time we were camped at high altitude (10-11K)  Too little air? maybe.