10 years from a CF 80 Waeco so far. I did have one problem, kept getting an error. Turned out to be an intermittently faulty fan. Total cost of fix was under $100 including labour. If you need it as a full zone freezer, just pull out the removable divider and turn it right down.
I built a couple of fridges and freezers for camping/boating. First one was a 130 litre freezer, with fan blower, Dometic components. I always build with fibreglass and foam insulation. Still running strong after about 8 years, does a lot of full time duty as a backup at home. The latest was a boat fridge. Danfoss compressor with a 3/4 radius coldplate, 50 litre capacity. My biggest problem is NOT having it freeze, you need to run it at the warmest setting. The electrics are mounted high, in an alloy housing, so you can hose around it. And it has a drain plug, something every fridge should have. :-) This isn't a cheap way to build a fridge, but nothing will rust, and I have a tailor made split lid so I can access one end without having to slide it out from under the seat frame it sits in.