Limiting respawns on scene

Hi there

I just wanted to know what is the cheapest way of instantiating prefabs at spawn points, whilst keeping control of how many objects are in the scene. At the moment i have this, but i think it might be too computationally expensive. :s Basically i want to spawn enemy soldiers at random points of the map, but i want to control limit it to soldierMax.

 #pragma strict
 
 var prefab:GameObject; 
 var soldierMax:int;
 private var soldierCount:int; 
 private var respawnPoints:GameObject[];
 private var maxSpawnDelay:int;
 
 function Start () {
      respawnPoints = GameObject.FindGameObjectsWithTag("SoldierSpawn");    
 }
 
 function Update () {
     if(soldierCount < soldierMax) {
         respawnSoldier();        
     }
     else {
         soldierCount = GameObject.FindGameObjectsWithTag("Soldier").length;
     }        
 }
 
 function respawnSoldier() {
     while (soldierCount < soldierMax) {
         Instantiate(prefab,respawnPoints[Random.Range(0,respawnPoints.Length)].transform.position,Quaternion.identity);
         yield WaitForSeconds(Random.Range(0,maxSpawnDelay));
     }
 }

Would appreciate the guidance :)

Thanks guys