At what age is a child's wishes considered when it comes to custody?

The only “magic age” in Nevada custody law is 18, at which time (absent a guardianship for incompetency, etc.), no one has any right to determine where the then-emancipated person can live.  Until then, the wishes of a “child of suitable age and discretion” are one factor that a court must consider when determining a question of contested custody.  For an explanation, links to the relevant statutes, etc., see the materials posted at http://www.willicklawgroup.com/child-custody-and-visitation/.