Hi Ioannis !

The longest line for a ds18b20 in my heating is about 35 meters.
The sensor line to my oven ( it is a small water-bearing oven which is in my living room ) is a Ymm 4x1.5mm˛ cable, because of the line resistance. Attempts with a network cable failed miserably for me.
I chose the smallest pullup resistance according to the data sheet. It is a 1k resistor.
My setup is working now for 4 years without any problems