Hi Marc,
LEDs have an extremly long lifetime. Your nor your camera will likely not be around by the time the LEDs expire. That said; regarding the motion detection issue: I would seem to me that in order for the camera to "see" in the dark to detect the motion, the LEDs would have to be on. That implies that if not always on in night mode, that they would have to be always on when in night/motion detect mode? You could easily test this out by enabling the night/motion detect mode, and watch the camera. The LEDs have a reddish color when they are on. Most of their emission is in the infrared spectrum, but their is some smaller emission in the visible red part of the spectrum.
Regards,
Bob