Concerning Ben Topin: I noticed. No complaint, but I noticed. The idea that your viewers didn't notice is bizarre.
The comment has me intrigued. You noticed that it's not Ben but Brandon instead? Or you can specifically tell which scenes needed to be reshot to include Brandon instead of Ben rather than the ones that were shot from the start with Brandon in the role?
I do find that odd, because frankly, most of US can't remember which scenes are which while watching it.
Though I am pretty sure the whole crew can see the ONE shot of Ben that was left in, and it wouldn't surprise me if that is the one shot you are talking about.... but not sure how to take your comment.
As for day/night... I think it's fair to assume that a starship decides on a specific time and then follows it from there...as we have seen the "ship's chronometer" which apparently establishes "ship standard time" despite where they travel. So, say Sulu is not rising to the dawn in San Fran while Chekov sleeps in waiting for the dawn in Saint Pete.
This is already being seen in the operation of the International Space Station. I could be wrong, but I've never seen those US men sleeping while the Russian guys were eating lunch already.
The human body really does need a day/night cycle for it's systems to operate properly. And the amount of daylight affects that in a real sense...something doctors and psychologists (of whom I am one) need to deal with on a daily basis.