Sometimes I leave a CRT monitor or TV on by accident for much longer than intended, occasionally even overnight, and I always feel this sting of guilt because, wouldn't it be a tragedy if I caused burn-in on one of the few devices of this sort still functioning, and the only one of its type that I personally have a shot at owning?
But the thing is, burn in was not a phenomenon that happened on that time scale. When you see a security camera monitor that has the date cooked into it, you have to remind yourself that that thing was on 24 hours a day for 10 years if not longer.
Back in the late '90s, I probably left my computer monitor turned on for a cumulative total of thousands of hours, with the Windows task bar and start menu present almost all that time, and never got any kind of impression in the phosphor. So, probably, you don't need to worry about this with something that you turn on every few weeks.
Needed to hear this. Everything will be fine.