Only burn in issue I ever had was from stuff I'd watch at "1.5X speed" on my Panny BD player.
Some programs would come with a non-removable "timing bar" at the bottom, and after a bunch of these in a tight time period, the bar burned into the screen.
However, that was on my Panny plasma - and...
How long have you used your LG 3D OLED?
I'm right at about 6 years and zero signs of burn in.
I kinda assume we watch similar content on our sets - ie, mainly movies on disc - and I can't imagine you watch yours much more than I watch mine, so I don't know why you'd have bad burn in and I'd...
Yikes.
I actually have a "backup" 3D set. I bought a 60-inch Panasonic plasma with active 3D in... 2013? Whenever they discontinued plasmas.
I got my current 65" LG OLED passive 3D in summer 2017 and it's been my workhorse.
Felt stupid buying a new set when the "old one" wasn't all that...