I thought I had it sorted out already: plasmas suffer from burn-in, LCDs (LED or not LED) do not. Than I looked into my Samsung user manual and read this on page 1:
Do not display a still image and partially still image on the LED panel for more than 2 hours as it can cause screen image retention. This image retention is also known as screen burn. To avoid such image retention, reduce the degree of
brightness and contrast of the screen when displaying a still image.Watching the LED TV in 4:3 format for a long period of time may leave traces of borders displayed on the left, right and centre of the screen caused by the difference of light emission on the screen.
Playing a DVD or a game console may cause a similar effect to the screen.
Damages caused by the above effect are not covered by the Warranty.
So now I am lost. Please help me understand - is burn-in a risk or not on LEDs?