I have a Sonoff S31 on my fridge for about 3 years now for power monitoing and have had no issues. I’m sure the fact I don’t switch it on and off and it’s locked to stay on on power up helps prolong it’s life. If you never switch the load I don’t see how it’s life could be impacted. But I do have a temp sensor on the fridge so any failures I would be alerted to.

My Aqara sensor has a pretty good signal in my fridge, results may vary as the material of fridges vary.