RE: Heat cycling
Yup many engines will never make it thru a full breakin process without replacing the Glow Plug. Heat cycling is just a term they use for short breakin process. You did good to keep it around the 190 heat range which means you ran rich. Heat Cycling calls for higher temps over a shorter period of time. Up and Down thanUp and Down with shorter runtimes.
A longer breakin procress will never hurt the engine shorter ones do. Some engine manufactures ask you to run rich for 8 tanks of fuel. I am a 5 or 6 tank guy then never really tune for performance until my 6th or 7th tank.