C9 is still pretty new, isn’t it? My C6 burn in is awful.
No sign of burn-in and I check it with color slides every few months. I think the C6 panels were much more prone to burn in than C7.
Some people with C7 panels had problems with a bug where the automatic compensation program does not run which greatly accelerates burn in, but I believe LG is replacing TVs for people who get that.
My C7 looks absolutely stunning with good sources 4k/HDR.
I'm happy with my purchase every day and would never think about going back to crappy LCD.