Burn in happens. I've got it on my Mark 1 from having the "Now and Next" display up for merely a couple months. It's faint, but it's there.

Is it possible to do a variant of the thing you just showed, adding multiple fields, altering both the X/Y position and the the "00:00" in each one, thus causing the time to move about the screen, yet stay on the screen the whole time?

If you bounced it around the screen's four corners, you'd reduce by 75 percent the amount of time it took to make a noticeable burn.