If you already have the courtesy lights I am sure it will not have any effect, the one thing to do would be to find out if it is switched power meaning is it powered all the time with the car off or if it powers up when the car is turned on, more than likely when the ca is turned on.
There are very few things that stay powered with the ignition off
Courtesy Lights
Clock
Headlights and taillights
Cigarette lighter
Emergency Flashers

Those are a few that come to mind