I haven’t seen any deformed or discolored primary W163 taillights, (The center light is a different story) but I’ve seen enough burned-up taillight lenses on other vehicles to have a strong aversion to mixing incandescent bulb heat and plastic.I agree leds = lower temp.
I my self have not encountered this on either of our mls but it probably goes with how long you leave your dome light on. Ours usually long enough to get in and start it, we don’t sit in it reading war and peace cover to cover.
As to tail lights I have never seen one deformed due to heat. Saw an ml fog light melted in the yard but they had modified it to a higher wattage bulb.
I did have on my GMC A.R.E cap a poorly designed switched dome light. Went through 3 under warranty they kept melting with the bulb they were designed for if left on for more then ten minutes. I just removed it though I would like to find an led switched strip light.
I do think LEDs have there place, just don’t think they are needed in tail lights and turn signals.