I purchased an Amish cooling unit 3 years ago for my norcold 4 door and still going strong.
Currently set to 5 and grill across the back is solid ice!
Rvcoolingunits now sell a 4 fan internal unit that spans the whole width of the fridge!
Ive been thinking of snaggin ng one.
I currently have the 2 fan setup i purchased and it is also still running after 3 years but it sounds like the bearings are on their way out.
For those of you that are looking into replacing the fan(s) just make absolutely sure they are pushing the air upwards!