I don't recommend using the headlights trick after turning off the vehicle. When I found this out, I would do it all of the time. But, I have had to replace both of my headlights. The nature of xenon's, it is not recommend to constantly turn them on and off. They will wear out faster, and reduce the life of the bulb. I can't find the reference to this, possible the owners manual?
(Edit)
Found it, Page 176 of the owners manual.