I will say that in most states, it's common for you to owe no more than two months past your break date, but again, consult your lease contract.
Additionally, in most states, if the owner releases the same unit to someone else BEFORE the time period (one, two or ever how many months) you paid extra for expires, the owner will be required by law to refund your extra payment.
This prevents the owner from collecting double rent on same unit.
Again though, check your personal lease