Gaming for a couple hours won't do anything.
LG's OLED TVs have a few methods by which to mitigate the potential for burn in, both when the TV is on and off. It's an important point that is often not discussed, and is something generally not seen in OLED monitors. And in my opinion, image retention is more of a serious concern than burn in. Most of the bad rap came from LG's early OLED TVs, like the 6 series. For example, the C6 scored a (terrible) 1.3 / 10 for image retention at Rtings back in 2016. Fast forward 3 generations, and the C9 scored a perfect 10 / 10 for (no) image retention.
If you do a few simple user-end adjustments like Kasakka mentioned above, you won't have any worry using OLED on the desktop or gaming.
And it's saying something I've uesed a c6 for my gaming rig till I updated to my c9 this year and never had any major burn in that I could see unless I uesed solid colored screens looking for it and it was very slight.....oled burn in is so over rated I uesed a pdp before and it/burn in was a thing on that. I feel as long as you don't leave it on the same game/desktop 24/7 you will be fine even playing poe for like 10 hours a day years ago never burned in on the c6