You can leave the control full on if you like. There have been no reports of induced blindness resulting.
Mercedes was an originator in auto features and terminology. I think they were the first to coin the term dark side in describing their electrical design of the cluster.
I still wonder what they were thinking when they designed the dash illumination. Worse yet on a car that prides itself on running production changes. It remained the same since introduction of production of that model over the years.
Thirty grand back then and you want to see the instruments at night as well? Perhaps it was just a common conspiracy. If you cannot see a slipping odometer it does not become a warranty issue as well crossed my mind. Or perhaps just an additional safety feature. What you cannot see again cannot hurt you.
Maybe they did not just want to overload the electrical system? One of my examples is unique. I have the optional very rare candlestick holders in front of the cluster.