I have tried really hard to detect any hint of image retention on my set, even when I've torture-tested it by leaving something up for "too long". I really have tried. I have failed.
Admittedly, I have tried to detect this against black or light/white background only. I do not maniacally go seek a USB drive with "slides" on it to see if I can detect the image retention against any and every primary. I merely attempt to see if the retention is discernible against any normal content that display, including transitions. And it has not been -- not even once.