I often drop the temperature at the first sign of 1st crack (FC) so that the time to 2nd crack (SC) is extended. But I dont drop to 180C that would probably be too low as you still want to "roast" the beans in hot air (which allows Maillard reactions to occur). Perhaps drop to 225C.
As to a difference betwwn run 1 and 2 - wait a week and then try them. Let us know what batch tastes better or what the difference is. I think a drop of 180 might be a bit low but it did extend the roast time so it may well improve the roast.
I often use 235 C till FC then drop to 228 C and end at SC.
As to your question if you drop the temp to 180 - the heater will turn off,
as the heater cools the air blowing past the heater and over your beans will drop in temp, then when the thermocouple at the end of the chamber (just above the exhaust) reads lower than 180C the heater will come on until its above 180 then go off again. The heater will just turn on/off to maintain 180C, the air will always blow until the Gene is < 60 C.
> What I want to know is does machine accelerate differently?
I dont know what you mean by that question.