I've been using OLED for a long time now, and never had this OLED burn in - including one particular phone (Ativ S, so Samsung S3 screen) that was in use by me for years and then used as a navigation system by my mother until the battery perished. However, someone I know had a phone (I believe the Samsung S8) nearly constantly playing videos with full brightness, and there it did show red streaks over the screen. I wonder what kind of usage triggers it.