Thats the temp that they melt the powder at. It's either 400 or 450. Either way, If the part gets hot enough again to remelt the coating, it could possibly loosen up, run, or whatever else might happen when something is in a liquid state. I think it would have to be around that temp for like more than 15 min or so for that to happen.

The brake rotors might be ok as being coated right up till someone decides to be spirited while driving through the mountains or twisty roads. I think a lot of hard braking might cause the coat to go bad.