The older the OLED the more susceptible. The newer ones use certain algorithms to freshen the screen. Some do it when you manually turn off the TV, some automatically at random times. If SONY TV's detect a problem you'll see a notification on the screen and they'll run a pass to free up stuck OLED pixels. Nevertheless, whenever you buy an OLED you must do three things once you get them home. 1) Change the visual mode the TV is in. Most are in a default Vivid or even a "Store" mode, which is like gunning your car engine all day. It'll shorten the lifespan of the OLED drastically. For LCD based TV's newly purchased, the picture will be unrealistically bright and washed out. That needs to be changed either to a Cinema mode or an equivalent, which lowers the temperature of the TV. Go online, search
Reviews and Ratings for proper calibration settings of your particular TV. 2) Update your TV via the internet. Go into the settings, set up your internet settings (I always plug in an ethernet chord, then switch to wireless once updated) and update your TV. Sometimes new TV's, OLED or not, won't work properly without the latest updates. Sometimes certain features are introduced after the TV is manufactured. Finally, 3) Baby your OLED for the first 100 hours at least. Avoid TV shows with stationary glyphs in the corners and/or information trails at the top or bottom such as news shows, or network shows that show the network call letters at the bottom right (ABC, NBC, etc.). Anything that shows stationary figures, boxes, or objects (such as video games) for long periods should definitely be avoided during the first 100 hours. After those 100 or 200 hours you'll be fine.