I can only tell you my own experience. Three Mobius that are all ~ 12mths old. One lives in the windscreen of a vehicle that is ALWAYS parked outside with no shelter- during Summer the outside temps reached up to 45 degrees C, 40 degrees C was very common. I'd hate to think what that would mean inside the vehicle, let alone at the windscreen. The case has not warped at all, even the battery has plenty of live left in it and hasn't bulged. A reflective sunscreen is normally placed inside the front windscreen, but the Mobius is not protected by it. (The Mobius is mounted on the rear view mirror arm, between the windscreen and back of rear view mirror.)
Perhaps the type of plastic used to make then has changed?
When the Mobius is operating, the heatsinks get too hot to touch - which tells me they are doing a great job at drawing the heat from the Mobius.