Good point Dennis!
I was teached to never run with any spotlight on other than docking for the same reason you mentioned and also as others can't see the navigation lights and that will eliminate the possibility for them to see where the boat is directed to.
As others already wrote, any forward pointing must be mounted in such way that it will not illuminate not the slightest way any part of the boat as it will reduce captains vision too much. And most likely the only point would be on the bow most foreward, but that is not the place i would like to have one installed. I have a spotlight, but as Skunk already mentioned i have a handheld but powerful flashlight to use in case of entering a total dark inlet/shelter, to search the water surface for something and once docked to climb off the boat.
I am very experienced in night boating and honestly i prefer to steer even in pitch dark than having a spotlight giving me a tunnel vision seeing only there where the spotlight points.
It may be that i boat in less complicated waters (ICW, channele, rivers, etc) than you do over there in US and the main risk is to run over a non illuminated fishing buoy i can't see at night. The other problem i have some times are dumbasses fishing in front of the harbour without or very weak illumination and for that reason i will install a radar in such way that he show me what is in front of my boat.
However, honestly i hate to drive back in pitch dark conditions, even if it happens sometimes, but i love to drive back with the moon illuminating enough to reasonable safe cruise slowly back to the marina.
Chris