Loading a scene with a long press!

 private float mouseDownTime;

 void Update()
 {
      bool hasBeenClicked = mouseDownTime > 0;
      if(hasBeenClicked)
      {
          bool timeHasElapsed = Time.time > mouseDownTime + 5;
          if(timeHasElapsed)
          {
               int s = Random.Range (0, SceneNames.Length) ;
               SceneManager.LoadScene(SceneNames[s]);
          }
          if(Input.GetMouseButtonUp(0))
          {
               mouseDownTime = -1f;
          }
      }
 }

 void OnMouseDown ()
 {
     mouseDownTime = Time.time;
 }