Problem Solved,
It took me a while but I finally found it.
I remove the following line in the setup:
EEPROM.write(500, thresholdSET);
It was overwriting my last settings with the default thresholdSET
at the beginning of the code.
int thresholdSET = 15;
I don't know why he did the code like that but now my settings stays
in the EEPROM until I change it.