An example of showing how to do a LeanTwee.moveSpline with better performance.

LeanTween Spline Performant

using UnityEngine;
using System.Collections;

public class EngineStressTest1 : MonoBehaviour {

	private int animateCount = 6000;

	private GameObject[] cubes;
	private LTSpline[] splines;

	void Awake(){
		LeanTween.init( animateCount*5 );
		int iter = 0;
		int side = System.Convert.ToInt32( Mathf.Pow( animateCount*1.0f, 1.0f/3.0f ) );
		Vector3 p;
		cubes = new GameObject[ side*side*side ];
		splines = new LTSpline[ side*side*side ];

		for(int i = 0; i < side; i++){
			for(int j = 0; j < side; j++){
				for( int k = 0; k < side; k++){
					GameObject cube = GameObject.CreatePrimitive(PrimitiveType.Cube);
					Destroy( cube.GetComponent( typeof(BoxCollider) ) as Component );
					p = new Vector3(i*3,j*3,k*3);
					cube.transform.position = p;
					//cube.GetComponent<Renderer>().enabled = false;
					cube.name = "cube"+iter;
					cubes[iter] = cube;
					splines[iter] = new LTSpline( new Vector3[] {new Vector3(-1f,0f,0f), new Vector3(-1f,0f,0f), new Vector3(0f,0f,0f), new Vector3(4f,0f,0f), new Vector3(20f,0f,0f), new Vector3(20f,0f,0f)} );

					iter++;
				}
			}
		}
	}

	void Update(){
		if (Input.GetKeyDown(KeyCode.T))
        {
        	Debug.Log("Starting");
            for(int i = 0; i < cubes.Length; i++){
				float delay = 0f;//iter*1.0f/cubes.Length;
				LeanTween.move(cubes[i], splines[i], 1.0f ).setEase( LeanTweenType.easeInOutQuad ).setLoopType(LeanTweenType.pingPong).setRepeat(-1).setDelay(delay);
			}
        }
	}
}