Burn-in is simply the uneven wear of pixels. For a pixel that is not on full brightness or turned off, it does not wear as much as the pixel that is on, even worse on full brightness. So, pixels in black bar area, those pixels don't wear as much as the pixels next to them displaying images. So the end result is you see the burn-in because the black bar area pixels are brighter than those not in black bars. Running slides wears down those otherwise bright pixels to even out by sacrificing the already limited panel life.
So, no, I personally never run such slides. Knowing full well to expect burn in before you buy the OLED TV is the best way to cop with it and play it safe during day to day usage, not just initial hours.