I know someone who uses an ancient samsung oled phone which they had left on overnight regularly for youtube for years and that had the faintest of burn in only visible on a pure white screen.

It's really not something I'd be concerned about.

That would depend entirely on how many hours you used it. They don’t age like meat, over time. They age from having current running through the pixels. So their degradation depends on the kind of content you watch, for how long, and how bright you configure the picture. I have thousands of hours on a 6-year-old OLED and it looks perfect, but I only watch films in a dark room so I don’t think it’s very demanding.

The Samsung Galaxy S III is 11 years old and had an AMOLED screen (does that still count as OLED?). People are still using them with custom ROMs somewhat, and I haven't heard of display issues.

There's also the first revision PlayStation Vita that had an OLED screen and is a similar age. I have heard of yellowing on some models, unsure how prevalent burn-in is. Of people I know with a Vita or several, most got a second gen only, or switched to a second gen and so the old one didn't get used as much.

Much less old, there's the Switch OLED, and WULFF DEN on YouTube has one he's leaving constantly turned on to see what happens to the screen. I think we're 1.5 years in or so and he's done a handful of videos showing what it looks like now.

https://www.youtube.com/watch?v=7TMyUDKqWWI

If you're using a 12 year old LCD panel, you're probably hobbling yourself with terrible resolution, response time, refresh rate, color gamut, viewing angle, backlight evenness, black level/contrast, etc.

It's absolutely bizarre how luddite HNers can be when it comes to keeping even remotely current on hardware.

My OLED is only 7 years old but has no issues so far.