RTINGS.com posted an interesting article, detailing the results of their long-term (10-months) longevity tests on several OLED and LCD TVs and monitors. The test is simple - display a CNN feed constantly, and checking what happens. Note that CNN changed their logo a bit a few months into the test, but the team did not make any changes to the test itself.
As is expected, OLED monitors and TVs suffer from image retention problems, and the CNN logo is visible in some of these panels, when showing a gray screen. Some TVs suffer more than others.
Something that may surprise many, is that LCD TVs also suffer from degradation over time. While this isn't the same burn-in problem as in OLEDs, there is visible uniformity issues, and as RTINGS.com puts it - "These uniformity issues aren't the same thing as burn-in, but in many cases, they're just as noticeable and distracting, if not worse.".
OLED monitors also suffer from burn-in. It is interesting that the team started to test ultra-wide (21:9) QD-OLED panels, and noticed that the burn-in is worse. This is because the CNN feed is 16:9, which leaves black bars on the sides of the screen. This causes the monitor to increase its brightness (in order to maintain the same average brightness level, or APL), and so image retention is accelerated (the brighter the image, the faster the OLED materials degrade).
Note that these tests are very extreme, these aren't usual watching patterns for most viewers, and so these results should not be expected in your own TV or monitor.
