Should I worry about..

Its a lcd screen, so no image "burn" is not possible. You can get image "persistence" which can cause colors in the area of the static image to distort but no image will be burned into the screen. Prolonged images on any display causes damage period. This is nothing new and its all about mitigating the risk. If you use the desk clock for long periods set the display to dim...that's why the setting is there.