Good question.
I just tested a ROP HI bulb/Modamag M2 LOP reflector combo and the side of the Mag lens bezel went from 69°F at start to 100°F after ten minutes.
At 15 minutes it was at 113°F.
The bezel was firmly wrapped with a strip of ¼ inch thick by ¾ inch wide neoprene to simulate the heat retention of the antiroll device and the temp probe was placed under the neoprene wrapper.