In a divorce decree that states a life insurance policy must be maintained while child is a minor. At what age is a child no longer a minor in Nevada?

Short answer:  18.  See NRS 129.010 Age of majority. All persons of the age of 18 years who are under no legal disability, and all persons who have been declared emancipated pursuant to NRS 129.080 to 129.140, inclusive, are capable of entering into any contract, and are, to all intents and purposes, held and considered to be of lawful age.