For some reason 500 days sticks in my mind, but that does seem too far in advance.
They will only guarantee the rate you pay after they have posted the new rates for next year. As an example the 2007 rates have not been released yet. You can book a site but the cost will be based on the 2007 rates weh they are released.
If you are looking at 2008 you can figure the rates will be published mid to late summer 2007.