PinkieLooks like you have to delete and recreate a new code when you add new items. Makes sense.
Just want to make sure you don't get started on the wrong foot here, but we don't quite follow what you mean?
If you'd created a Discount Code with Max Use Count=1, then that code could only be redeemed once, ever; that code would become invalid after the first order is completed where that code was redeemed. If you create a product-specific discount code and then delete the product it was created for, then that code would become invalid as well.