If you're visiting the parks for 8 days, then an annual pass might be the least expensive way to go.
An adult AP would cost you around $393 with taxes. If you're staying onsite, a UPH for 8days/7nights would be $380.21 (if purchased in advance). However, if you wait until you check in to purchase it so that you can drop your first or last day, the price rises to $408.
If you're staying offsite, then you're going to need 2 4day PHs. If purchased in advance, they'll cost you $409 for the pair. The AP would still be cheaper.
If the FITS tickets come out with expiration dates that go beyond May, 2004. Then that would be your best value. You can always wait and hope.