Is this the best way to do an AutoParallax Background ?

Hello everybody,
I’m developping a game that require a Background that scroll in a infinite loop and so I did this:

public GameObject prefab;
		public float width;
		public bool alreadyDid;
		public float speed;
		public string name;
		private Camera camera;
		public float cameraWidth;
		public float cameraPosition;
		public float xLastFrameSprite;
		public float xFirstFrameCamera;

		// Use this for initialization
		void Start ()
				SpriteRenderer sprite = gameObject.GetComponent<SpriteRenderer> ();
				width = sprite.bounds.size.x;
				alreadyDid = false;
				camera = Camera.main;
				cameraPosition = camera.transform.position.x;
		// Update is called once per frame
		void FixedUpdate ()
				cameraWidth = renderer.bounds.size.x;
				transform.Translate (new Vector2 (-speed, 0) * Time.fixedDeltaTime);
				if (transform.position.x < 0) {
						if (!alreadyDid) {	
								Vector2 v = new Vector2 (transform.position.x + width - 0.1f, transform.position.y );
								Object obj = Instantiate (prefab, v, Quaternion.identity); = name;
								alreadyDid = true;
				xLastFrameSprite = gameObject.transform.position.x + (width / 2);
				xFirstFrameCamera = cameraPosition - (cameraWidth / 2);
				if (xLastFrameSprite < xFirstFrameCamera) {
						Destroy (gameObject);

And it works very well but I wonder is this the best way or I can approach it in a different mode ?

This is almost the same way i did it and it seems pretty efficient but when I added 4 layers of sprites with transparency, the performance drops signficantly. Is there a shader or some trick to add screen-size sprites with transparency?