My brother has a LG E6 and it has bad burn in because he watches news channels a lot and it's only 4-5 years old but the burn in happened maybe 2 years ago so it only took 2-3 years. I'll never have that problem because I don't watch the news.
Honestly lg e6 is ancient compared to tvs now. A lot of it is under the hood, but Improvements happen as such a rapid pace that a tv that came out in 5 years ago is not comparable to a tv today. Technology improves and progresses that fast.
I wouldn't buy a tv on a hope that maybe sometime down the road in the future 8k might possibly, one day sorta would be used for something. Right now it is a gimmick, and if or when actual 8k content, or a use for it materializes years from now, that 8k tv you bought this year will be way behind those new, modern 8k tvs