Are there time limitations on yield WaitForSeconds?

I have a triggered instantiation with yield WaitForSeconds in front of it. It works fine with a wait of 15 seconds. It works fine with a wait of 25 seconds. But for some reason, 30+ seconds, it won't call the instantiation.

its on a non-deleted independent object..code as follows...

  function DelayspawnerMagicPill(){
 
           yield WaitForSeconds(35);
         var randomPick4 : int = Mathf.Abs(Random.Range(0,spawnlength));
         var DsMP : GameObject =  Instantiate(MagicPill, spawn[randomPick4].position,spawn[randomPick4].rotation);
         
         var spawnJS4 = new Array() ;
         spawnJS4=spawnCopy;
         spawnJS4.RemoveAt(randomPick4);
         spawnCopy =spawnJS4;
          spawn=spawnJS4;
 
             }