It’s worked so far and by keeping the pixels “working” and changing constantly it should eliminate the possibility of screen burn. Dimming the screen means the pixels aren’t working quite as hard.
Wait, how does a screen suffer like this from about 3 hours of usage? I think you should get it repaired under warranty as it is almost certainly a defect on the manufacturer’s part or get a new device. BTW, what brand and model is it?
Dimming the screen on a standard LED backlit screen makes no difference, they are all lit the same way and the pixels just hide whatever light needs to be hidden.
Advice given of the scenic cam + auto hide are the best. Note that it will probably go away over time.