I have a 65" LG OLED (2017 model) and I have not seen any sign of any burn-in ever.
The LG OLED replaced a plasma-- and I was just a bit concerned the picture would not be as good as the plasma. I so pleased that it was actually BETTER. I actually changed to the OLED for the sound processing. New TV, new Denon receiver, and nine new speakers. While the picture is amazing-- the sound (with a suitable source) is my favorite thing about the new set up. The Dolby ATMOS & DTS:X are great (just not enough content yet).