Then you do realize the part that burns in is the same exact thing that burns-in on an LCD TVs, right? (same exact material)
This quote is talking about OLEDs, but it is the same across both.
Basically, it amounts to a sort of stain on the display material that alters the color displayed.
You are also aware that lower power consumption of newer TVs is what helps lower the chances of a burn-in affect in both LCD and LED (and Plasma for that matter!) So, while I don't know if you actually let your TV sit for 12+ hours with a static image; if your TV is newer, it will be more resistant to burn-in due to lower power consumption.
If you think your LED TV is burn-in proof, you're a fool.