Clarification question ~ are you limited to using only $100 credit per cruise even if you purchased more?
Good question! As far as I know the On Board Credits are per Stateroom/Cabin. At least unless they have changed it. I've been told in the past that you could use the $100 off the balance on a per person basis with each person having a certificate, but the OBC's were based on the cabin.
is a link to one that looks similar to the one that I had a few years ago. Note the fine print at the bottom.