If you put some form of boil breaker, ie, bits of brokem porcelain or copper, even small quartz pebbles you can tell by the sound how the boil is going. I still have a thermometer in my kettle but never use it. I guess it's nice 'eye candy' as someone said to me a long time ago. Do it if you wish, the choice is yours.
Simple potstiller. Slow, single run.
(50 litre, propane heated pot still. Coil in bucket condenser - No thermometer, No carbon)
The Reading Lounge AND the Rules We Live By should be compulsory reading
Cumudgeon and loving it.