For my 36c the weakest point is the fridge insulation. So far i have cleaned condenser, evaporator, fans, replaced thermostat twice and fiddled with the settings of the compressor.
I went through the process of making a pressure test initially then refill the system with fresh freon. My evaporator fan is wired to be permanently on. In my opinion the the tradeoff is worth while to keep the system working correctly.
My initial capillary tube thermostat was jammed in the evaporator plate, basically sensing the surface temperature of the evaporator. Short cycling was an issue and i have currently replaced it with a 12v electronic thermostat with adjustable hysteresis with the sensing probe located near the shelf in the fridge. Since tuning of parameters i am now getting 15-20 min run time and 1h off, 8 degrees setpoint, 3 degrees hysteresis and ambient 15-20.
Top lid had no gasket and i kind of improvised one although not completely happy about the fit. The worst part is the open cell foam insulation around the fridge box which i am sure is soaking up humidity (dew point). There is no easy way of removing the box and re-insulating it and most likely it will require re-tubing of gas lines and loss of freon. If i were to do redo everything i would install quick connectors on both sides and use normal evaporator plate, not the flimsy aluminum finned one. It makes cleaning very easy and less chance of mold growth.
Few years ago designed a custom made fridge for my old boat, out of Okume plywood and foam core panels (like for PVC windows). Did my math and ended up with a good balance between internal volume and efficiency and it worked great with minimum power consumption (4 A, 12 minutes every 1 hour). It did help that the lid had double gaskets and latched closed keeping a good seal.
As for the compressor and electronic unit, mine are located under the saloon bench seat and do not warm up the fridge compartment. They are very reliable and have lots of features like over/under voltage protection (compressor trips if you drop below a set voltage), motor speed adjustment (better efficiency in some applications). The diagnostic pin can also be wired and can tell you by a series of flashes if you have any issues with the system.