JFI2089WES Jenn Air fridge and freezer no longer cooling

[kero]

Hello,

We came home from being away for a few days and had to throw out everything in our fridge and freezer. We think this is a 2010 model but it's worked perfectly up to this point.
Lights are on but no other sound that indicated it was working. Since it was the weekend we had to wait for a service technician to visit.
When we pressed on the LCD display a blank blue screen lights up and the buttons are not responsive. Power shut down and restart did not fix anything.

In the next 3 days, we left it be and it came back to life twice on its own (including beeping the temperature warning and making ice for about 24 hours) before dying again. When the technician from Whirlpool showed up, it was actually working and cooling just fine.

The technician proceeded to check and change various settings on the panel, called into Ohio to explain our issues and concluded it's either the control board (60%) or the UI (40%). He did not take apart anything to test at all. UI he explained is discontinued so we can only try replacing the control board. And he also said whether the unit was working or dead during his visit does not change his diagnosis.

Since he left, the unit died again and had stayed dead for the last couple days (lights still on).

I have a few questions that i hope you can help with:
1. The service call we paid for included follow up calls with no extra charge within a time period. Was there something he could have done more to be more sure where the problem came from.
2. Currently it feels like a bit of gamble, to spend a few more hundred bucks to replace the board that's not returnable. What's the best way to narrow down the culprit - board/UI/something else altogether?
3. If it is the control board and we replaced it - how much longer is the realistic time the unit's life can be extended?

Thank you in advance!