Should landing light be off during line up and wait position?
Counter-intuitively, the FAA answer (see chart on page 1-9 and text on page 1-10) is actually, they should be off during the line-up-and-wait phase.

When cleared to ...


  “Line up and wait”—when entering the departure
  runway without takeoff clearance, turn on all exterior
  lights (except landing lights) to make your aircraft
  more conspicuous. 


Then when takeoff clearance is received, the expectation is that landing lights will be turned on.

The best rationale I've seen for this is so that Tower controllers (and other aircraft) have an immediate visual cue that an aircraft "on the numbers" understands that it has been cleared for takeoff, or not.

Another FAA document, SAFO 11004 (these are "best practice" recommendations, not requirements):


  Exterior Lighting:
  
  o Taxi with taxi light on when moving, off when stopped.
  
  o Turn on all exterior lights when crossing any runway.
  
  o If cleared to “Line Up and Wait”, turn on all exterior lights except landing lights.
  
  o When “Cleared for take-off”, turn on all exterior lights, including landing lights
  
  o If you see an aircraft in take-off position on a runway with landing lights ON, that aircraft has
  most likely received its take-off clearance and will be departing immediately.