GTP temperature

My 2 and a half years old male GTP seems to be resistant to temperature changes. He has a cool side and a warm side in his glass enclosure. I am heating the warm side with a ceramic heat bulb and i can,t tell exactly how high the temperature at the warm side is because i have the thermometer at the cool side. But it,s definitely below 88f. At the cool side its about the room temperature which is between 76-80f. He seems to change his place between the two sides not according to the temperature. While my BCI now in November spends many hours during the day on the warm side, my GTP chose to remain on the cool side for about a week now. He is totally healthy and very active at night. Yesterday he ate a live large mouce

I don,t think that i have an extraordinary GTP. I just had no experiences before with GTP,s. I was suprised to find out that they are not as sensitive about temperature as i have read about them. Maybe babies and Juveniles are more sensitive. I got my GTP as he was subadult. He was born in 2015 but i don,t know exactly when because the day and month of birth are not written on his birth certificate, only the year which is something not normal. The most sensitive snake that i have to temperature changes is my BCI. He is dependent in winter on his heat source.