I'm not so sure that's true. The mitigations they're doing seems to work very well for all sorts of form factors. I've been using a dell UP3017Q OLED monitor as my main display for most of last year and haven't had any issues so far whatsoever. It's simply the best display I've ever used. Even for my LG OLED tv, which I've had for a couple of years hasn't exhibited any image retention issues at all, despite watching a lot of news with scrolling headlines and logos. I wish OLED monitors would become more generally available since they're far, far superior to LCDs but for some reason apart from a limited run of the Dells and some short lived laptop models they're pretty much nonexistent.

> the screen isn’t on with static elements for 8 hours

I have two old cellphones mounted on the wall in my house that show time, weather, control the thermostat, etc. Most of the display is static. After a couple of years the burn-in is dramatic. I was surprised as I thought only phosphors burned.

I can attest to the OLED burn-in. My three-year-old Samsung Note 4 has a very noticeable bar across the top, from the dark status line above what is usually a light background on everything else. I guess the rest of the screen is what is burnt in and the status bar area is closer to its original state.

I don't notice it most of the time, but it really stands out on anything full screen. I think I would be rather annoyed if a three-year-old laptop did this.

It depends: I've got a Samsung S II with OLED and it doesn't show any flickering. But also a later Samsung also with OLED from all I can tell, and it does, and sat together with someone else trying to figure out what's going on. My interpretation is that early OLED displays were always running 100% duty cycle, but instead would lower the current through each pixel for lowering the brightness (when dimming the S II very low (and adapt your eyes), you can start seeing artifacts, i.e. pixels being lit up less precise because they are in fact using the lowest few values available of the current range). For later phones it appears Samsung added a PWM on top of it, so as to be able to dim the display independent of the pixel currents, perhaps to get rid of these artifacts in low brightness settings, or possibly because this might be a bit more power efficient.

What can be done, apparently (as my friend found out searching the internet), if you've got root, is to install a kernel driver to set the PWM duty cycle to 100% and instead use the old per-pixel dimming approach. I haven't bothered (not using my phones enough) but something potentially worthwhile to do if you use your device for a lot of (book) reading.