Regarding your question, it depends how ST processes your iPad. Basically what happens is if you need to make a claim, you contact them and they have you send it to their repair center. Their engineers will look the item over. If they can fix it, they fix it and send it back to you. If they cannot fix it (which seems the more likely course of action with a cracked iPad screen, I would think), then they issue you a check for the full purchase price you paid.
So if you get the check, I think it's pretty obvious that your coverage ends there insofar as you are no longer in possession of the item. Now, if it's the case where they repair your item and send it back to you, are you still covered? No idea.
I spoke to a sqauretrade rep regarding this matter. You are covered up to $599. Meaning that if it costs $100 to repair a screen, they can repair your screen 6 times. They deduce whatever each individual repair costs from the $599 purchase price. The result is how much coverage you have left going forward.
If you damage it and it costs $200 to fix.. they send it back to you after they fix it, and now you are covered up to $400. If you destroy it, they send you a check for $400.. If you damage it but they could fix it, they will cover repair costs up to $400.