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if your mother has hot water base board heat... well you cant adjust it as frequent as forced air.

simple is better:
if vision is the issue get a Honeywell round thermostat and (diy) put a mechanical stop so she cant adjust below 68F
 
I use the Nest with it's app, very handy set temps when in bed! I don't know how tech savy your mother is but I would look into a thermostat that is programmable with different temps during the day/night. Once it is set up for her, she should be comfortable. The nest loses it't network connect every now and then and it constantly wants me to use Google log in. I got the Nest before Google bought them, and don't anything to do with Google in my home network.
 
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