Anticollision - all the time, of course.
Position - only when it's dim enough that they are visible, otherwise, what is the point, really. At night on shutdown, they stay on to help mark the tail rotor.
Landing - on the way into the airport. Once in the pattern, it goes off. At night, used as needed.
Of course you can leave all the lights on all the time, and maybe it would give you that 0.0027% edge. On the other hand, staying late to replace the burned-out aft position light might make you 0.92% less sharp the next morning...
...man this Fetzer Bonterra Chardonnay is tasty!
