LCD Burn In Question

I would like to prevent a static image from burning in on a 1.8" LCD screen, by setting a timeout to turn the LCD off when there is no motion detected. Could I check if I need to turn the LED off, AND fill the screen blank(ie fill black colour), or could I just turn the LED off to prevent this.

I believe the crystals need to be changed for it to be effective, so filling the screen would be needed, but I need a confirmation, as I would be bloating the code if there isn't a need.