I just tap the play key on the remote and bring up the green progress bar for elapsed time if I need to. Clocks are similar to channel logos on the corner of screens, you're OK if you switch channels and don't stay on one channel all the time and turn the brightness down. For the clock just turn it off after a few hours and don't let it run. Burn-in used to happen with CRT tubes also long before OLED. Games that used stationary images on the bottom of the screen would burn-in. The advice was turn the brightness down if you play the same game for a long time.Thanks - I agree OLED's are more prone to burn in - just hoping to hear from someone who might know for sure.
And I find not only the clock convenient on screen, but the elapsed time when playing back a recording.