From what I've learned about general OLED burn-in is the higher the brightness the sooner burn-in will appear, but even at 60% OLED brightness burn-in will eventually happen. Plus red OLED pixels damage sooner, which is why newer OLED TV's have bigger red pixels.
That's blue OLEDs. Blue OLEDs are less efficient than green or red which is why the blue subpixels are larger on samsung oled panels, for example, as they need to be driven with a higher current to match the luminescence of the other two. However, that doesnt apply to LG's TV OLED panels as they dont used coloured OLEDs - they use White OLEDs with coloured filters on top. White OLEDs last longer but the use of filters also leads to lower luminescence which is why LG's TV panels have a 4th subpixel which is pure white to boost brightness. The subpixels are still different sizes, but that's more to do with colour accuracy than lifespan.
My E7 still going strong, bought in October 2017
2 years isnt any age for a TV, id absolutely expect it to be tip top