Version: 2018.1
public float duration ;


The duration of the particle system in seconds.

This property can only be set when the particle system is not playing.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour { private ParticleSystem ps;

void Start() { ps = GetComponent<ParticleSystem>(); ps.Stop(); // Cannot set duration whilst particle system is playing

var main = ps.main; main.duration = 10.0f;

ps.Play(); } }