> I've never even seen burn-in on anything other than a signage TV, and that happens even on some LCDs
AFAIK, the hardware still suffers from that problem, but it's been fixed in most devices by software fixes. Instead of displaying the exactly same content 24/7, it has "cleaning programs" or similar to runs once in a while to prevent the burn in from happening. Our OLED TV does the same I think too.