eykatz Cloning them is going to take a considerable amount of time. Try greenthreading this behavior, so that the task isnt blocking the main thread from continuing.
Heres my example of an asynchronous loop. You can loop through countless iterations without clogging up your thread or using a worker.
https://github.com/Dimensionscape/Starling-AsyncLoop
Example usage in main.as
In your case, you might want to create your objects in a worker thread, and then use the async loop to clone them on the main thread, but you could potentially do both in the main thread without blocking using this technique. It is especially helpful if its not important when the task finishes in relation to the scope of other linear behavior.
Notably, this technique can be adopted for pure flash api usage with a few additions and modifications particularly in implementing a delayed call outside of starling.