Also, I have had the ranco 111000 apart, and the only moving part I see in there is the relay that switches power. The rest is solid state. Relays can fail, but mine only switches on/off every 10 minutes to 30 minutes (Depending on heatsinking and insulation of the tape, and temp of the room.), and has redundancy.
As previously mentioned, you can have the features of a proportional and some redundancy by just putting a ranco upstream of your proportional t-stat.
Just don't try putting 2 proportional t-stats in series, as one will kill the other. (They're territorial.)
I think some herpstats can be used in this fashion, but you'd give up some features.

I will note that I AM OCD (No lie.), but I just don't see the sense in having any temp controller watching a rack of snakes that could cost thousands of dollars, without some redundancy or failsafe.
Yes, I also have a UPS on my rack. A APC SU2200RMXL with the optional SU48RMXLBP battery pack. I was out of power for several days last winter, and that UPS saved my bacon.

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