Destroying a gameobject clone after a time

Here is my code for spawning multiple enemies forever. The level changes if they kill the player. How can i get it so that if the cloned objects collide with something then its deleted without causing errors i know to use something like this

 using UnityEngine;
 using System.Collections;
 
 public class trigger_Destroy: MonoBehaviour {
     void OnCollisionEnter2D(Collision2D coll) {
         if (coll.gameObject.tag == "floor")
             Debug.Log("destroying enemy...");
             Destroy(gameObject);
         
     }
 }

But of course it wont work as the object the script is using is being deleted.. im stumped really. Not to sure on where to go. Any help is always appreciated.

 var theObject:GameObject;
 var maxPosx:float = 2.898618; // x axis
 var minPosx:float = -1.89557; // x axis
 var delay:float = 0.5; // delay each spawned item by 0.5
 var maxPosy:float = 5.086665; // y axis
 var minPosy:float = 5.086665; // y axis
 
 
  
 function Start(){
     StartCoroutine(spawn());
 }
  
     function spawn() : IEnumerator {
         for (;;) {
            yield WaitForSeconds(delay);
            var theNewPos= new Vector3 (Random.Range(minPosx,maxPosx),Random.Range(minPosy,maxPosy),0);
            var go : GameObject = Instantiate(theObject);
            go.transform.position = theNewPos;
         }
 
     }

EDIT: What if i added

         Destroy(theObject);

Which would destroy the cloned object that isnt needed? Im not on unity now but would this work in theory?

If you know of a way that i can edit this script to remove the spawned objects after a time i would appreciate it.