Latest from the factory on this:

Don't wash the car when the car is hot. If you do so the calliper may stick. If you do have to wash the car when it is hot, move the car backwards and forwards an hour or so later. This should free up the calliper. If the calliper does stick on it may result in a calliper mark on the disk, causing vibration. The disk may then need to be skimmed. The labour costs to do this and then bed in the disk may be more than fitting new disks, assuming you need a garage to do the work for you.