There’s nothing like hard proof to put a person’s mind at ease. So, to do just that, we strapped down a 20 foot extension ladder to the roof rack of our 2004 Prius and drove around and around for 7 days (so far). All the snow, rain, 120+ miles, including this extremely bumpy section of road, and vast temperture swings have not had any effect on their worthiness. They are still tight.