Entire cooling shut down - restarted 10 hours later, shut down again 12 hours after restarting.

Hi and welcome to FixYa, I am Kelly.

The defrost cycle is usually terminated by a 60 Deg bi-metal thermostat. If the defrost heating element is not heating up the unit will shut off until the internal temp reached 60 Deg F and then restart.

Defrost cycles are 10 - 12 hours apart depending on the defrost control installed so that explains the 12 hr repeat. I really think you have a bad defrost heating element. Here is why I say that...
1. The Defrost cycle is 12 hours after last defrost. (Means the defrost control /board is working)
2. The defrost cycle terminates at 60 Deg F
3. No working defrost element will cause very very long defrost cycles due to the time it takes for the compartment to warm up to 60 deg F and terminate the defrost cycle.

The element is item 33 of this link:
http://www.appliancepartspros.com/partsearch/model.aspx?model_id=5164987&diagram_id=28252332#d28252332

Just looking at the drawing it appears that the Defrost heater and defrost thermostat are an assembly.

You should be able to read resistance end to end on the heater assembly. If you have no resistance it is most likely open / has failed.

The defrost thermostat will read resistance anytime compartment temp is BELOW 60 deg F.

Thanks for choosing FixYa.
Kelly