I like to break down monster forms into smaller forms where page 1 submits to page 2 and hides its input in hidden fields. Each individual page takes less time to fill out and the final submit would be processed the same way you do it now.
Another option is a hidden frame that refreshes the session while they are filling out this form.
Option 3 is to either hack or brilliantly code something together that sources the submit page from the login submit page. (the same idea as the internal redirect. if there is internal redirect code out there that would most likely be preferred)
