Keep doing Coroutine even when destroy game object ??

Invoke coroutine from another script. I usually use the couroutine manager, which is attached to the always active gameObject. Below is the CoroutineManager script. Add it to the always active gameObject.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class CoroutineManager : MonoBehaviour
 {
     static CoroutineManager instance;
     public static CoroutineManager Instance { get { return instance; } }
 
 
     private void Awake()
     {
         if (instance != null && instance != this)
         {
             Destroy(this.gameObject);
         }
         else
         {
             instance = this;
         }
     }
 }

I created a sample script showing that coroutine will be executed correctly even after destroying the object.

Add the Example script to some gameObject. This gameObject will be destroyed after 1 second. Assign another gameObject to the "efect" field. This gameObject will be destroyed after 2 seconds.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Example : MonoBehaviour
 {
     // reference to "efect" I want to destroy
     public GameObject efect;
 
     void Start()
     {
         //we call ExampleCoroutine and pass references to gameObject "efect".
         CoroutineManager.Instance.StartCoroutine(ExampleCoroutine(efect));
 
         // after 1 second gameObject with this script will be destroyed
         Destroy(this.gameObject,1);
     }
 
 
     IEnumerator ExampleCoroutine(GameObject efect)
     {
         yield return new WaitForSeconds(2);
         // after 2 second we destroy "efect"
         Destroy(this.efect);
 
         while (true)
         {
 
             // we display log to show that coroutine is living
             Debug.Log("I live!");
             yield return  null;
         } 
     }
 }

The @unityBerserker's answer is good. But if all you need is to destroy an object with a delay, you can simply call Destroy(this.effect, 1f); It's a built-in delayed destroy