How long do you "not" look out at a time and think it is safe to do so?
I notice you ignored a reasonable question.
Care to explain how long you think it is fine not to look outside when VFR/VMC?
Of course there are weaknesses of the ol' eyeball...but not looking out really does negate what usefulness it does allow....or did I miss something in all those years of flying?
In your three crew operation how do you divide Cockpit duties that would required all three to be focused inside for very long?
At altitude in cruise...knowing the eye's inability to focus much beyond the nose of the aircraft...and the closing rates of Jet Aircraft....it is hard to see other traffic until too late. Add in obstructions to vision and it gets more difficult yet.
In a terminal area during approach in VFR/VMC conditions where there is a lot of traffic it would seem self preservation would suggest keeping as sharp a lookout as possible would sound acceptable to you.