Booking on board and 4 day discounts

[smchan]

I booked a April, 2005 Eastern while on board earlier this year and I'm more and more certain that I won't be going on that cruise as I have the May, 2005 repositioning booked as well. (I booked the 4/2005 cruise back when the PC cruise was just a rumor.) For booking onboard, I received a 10% discount and $200 shipboard credit. I understand I can't apply that discount and credit to the PC cruise.

So... I want to take my family on a pre-Christmas cruise - either a 4 or 7 day. Assuming I transferred the reservation to December to a 4 day cruise, are there discounts or benefits?

Thanks,
Sam