I am used to this on my Princess sailings. I was suprised that I had to pay up front when I booked my upcoming cruise on the Explorer due to my time dining.
Explorer of the Seas October 2013
Caribbean Princess July 2006, May 2010 & November 2012
Monarch of the Seas November 2008
Crown Princess November 2007
Celebrity Zenith November 2005
Enchantment of the Seas August 2004