SSCacheManager.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class SSCacheManager : MonoBehaviour 
{
	Dictionary<string, List<GameObject>> m_Cache = new Dictionary<string, List<GameObject>>();
	Dictionary<string, List<GameObject>> m_Using = new Dictionary<string, List<GameObject>>();

	private static SSCacheManager m_Instance;
	public static SSCacheManager Instance
	{
		get
		{
			if (m_Instance == null)
			{
				m_Instance = Object.FindObjectOfType(typeof(SSCacheManager)) as SSCacheManager;

				if (m_Instance == null)
				{
					GameObject go = new GameObject("CacheManager");
					DontDestroyOnLoad(go);
					m_Instance = go.AddComponent<SSCacheManager>();
				}
			}
			return m_Instance;
		}
	}

	private void Awake ()
	{
		if (m_Instance == null) 
		{
			m_Instance = this;
			DontDestroyOnLoad (gameObject);
		} 
		else 
		{
			Destroy (gameObject);
		}
	}

	private void OnEnable () 
	{ 
		if (m_Instance == null) 
		{
			m_Instance = this;
		}
	}

	private void OnDestroy () 
	{ 
		if (m_Instance == this) 
		{
			m_Instance = null;
		}
	}

	public void PreLoad(GameObject prefab, int quantity)
	{
		string n = prefab.name;

		if (!m_Cache.ContainsKey (n)) 
		{
			m_Cache.Add (n, new List<GameObject> ());
		}

		for (int i = 0; i < quantity; i++) 
		{
			GameObject go = CreateObject (n, prefab);
			go.SetActive (false);
		}
	}

	public GameObject InstantiateObject(GameObject prefab)
	{
		string n = prefab.name;

		if (!m_Cache.ContainsKey (n)) 
		{
			m_Cache.Add (n, new List<GameObject> ());
		}

		if (m_Cache[n].Count == 0) 
		{
			CreateObject (n, prefab);
		}

		// Remove from cache
		GameObject r = m_Cache [n] [0];
		m_Cache [n].RemoveAt (0);

		// Add to using
		if (!m_Using.ContainsKey (n)) 
		{
			m_Using.Add (n, new List<GameObject> ());
		}
		m_Using [n].Add (r);

		// Active object
		r.SetActive (true);

		return r;
	}

	public void DestroyObject(GameObject go, float time = 0)
	{
		StartCoroutine (IEDestroyObject (go, time));
	}

	private IEnumerator IEDestroyObject(GameObject go, float time)
	{
		if (time > 0) 
		{
			yield return new WaitForSeconds (time);
		}

		foreach (var item in m_Using) 
		{
			if (item.Value.Contains (go)) 
			{
				// Deactive object
				go.SetActive (false);
				go.transform.parent = transform;

				// Remove from using
				m_Using [item.Key].Remove (go);

				// Add to cache
				m_Cache [item.Key].Add (go);

				break;
			}
		}
	}

	public void Clear()
	{
		// Clear cache
		foreach (var cache in m_Cache) 
		{
			foreach (var item in cache.Value) 
			{
				Destroy (item);
			}
		}
		m_Cache.Clear ();

		// Warning if using
		if (m_Using.Count > 0) 
		{
			Debug.LogWarning ("Some of gameobjects which have been using will not be destroyed");
		}
	}

	private GameObject CreateObject(string key, GameObject prefab)
	{
		GameObject go = Instantiate (prefab) as GameObject;
		m_Cache[key].Add (go);

		go.transform.parent = transform;
		go.transform.localScale = Vector3.zero;
		go.transform.localPosition = Vector3.zero;
		go.transform.localRotation = Quaternion.identity;

		return go;
	}
}

A useful cache manager which is made by myself.