I've had an LG B9 OLED since late 2020, and I use it relatively infrequently (maybe like 2h per week on average, mostly movie or TV show content, rarely anything with fixed UI or logos). It does have some noticeable non-uniformity but but only when it's on a uniform dark-grey screen. When it's displaying actual content, it's not visible (unless your content happens to be a uniform dark-grey screen).

The burn-in pattern is a sort of inverse vignette, where the edges of the screen are brighter than the centre. Presumably, the middle of the screen sees more action in general.

I have a B7 from 2017 with a similar usage pattern as yours and it still presents movies and shows wonderfully. I think most people use theirs quite a lot more though.