^ Definitely removed the bright blue film that protected the unit from scratches in transit before fitting, all vents were clear. It got very hot in operation, and when it started to go the unit emitted a high pitched buzz and the video feed had lots of blotchy purple bleed on it. The unit status female voice went crackly too. If any of those start to happen then your unit is on its way out.
The rear unit didn't get hot at all - I do think the way forward with dashcams is a well ventilated base unit you can keep in a place out of direct sunlight, attached to satellite cameras that stay relatively cool.