Thanks for your answer. That helped a lot. About the purchases adding to the cruise credit days, we did know that but thanks for verifying that for us.
We'll make the bookings ahead and get a preliminary bill a few days before the cruise ends.
February 2008: HAL Zuiderdam: Eastern Caribbean
November 2009: HAL Noordam: Caribbean Wayfarer
November 2010: Norwegian Jade: Western Mediterranean
January 2012: HAL Eurodam: Eastern Caribbean
May 2012 HAL: Noordam: Transatlantic Riviera
HAL Westerdam: Panama Canal