Question related to optimization in unity3d

Hi

I am new to unity, I am working on a 2d game. I have created a background that scrolls infinitely over time. For that I have created a plane as a game object and assign it a material and to that material I have assigned a texture. now I change offset of the texture every frame through a script. It looks fine when the game starts but if I let game running for about 30 mins or so it starts showing waves in the background here is my code

 public class BackgroundManager : MonoBehaviour {
     
     public int materialIndex = 0;
     public Vector2 uvAnimationRate = new Vector2( 0.0f, 1.0f );
     public string textureName = "_MainTex";
     public float speed = 0.5f;
     Vector2 uvOffset = Vector2.zero;
     
     // Use this for initialization
     void Start () {
 
     }
     
     // Update is called once per frame
     void Update () {
         uvOffset -= ( uvAnimationRate * Time.deltaTime * speed) ;
         if( renderer.enabled )
         {
             renderer.materials[ materialIndex ].SetTextureOffset( textureName, uvOffset );
         }
     }
 
 }

An Edit: I will be deploying this code to android/ios devices. please help