We just got off a 4 night sailing on the Magic with no sea days- it was only available 1 day to us. I think it depends on the cruise itinerary and the ship. For a 5 night, I would expect 2 days (but could be wrong).
I think I read where someone answered, but we were out of Miami, went to Key West, Nassau then CC. I would have rather had the Dream's Nassau, CC and sea, but we had a friend that was worried about sea sickness (and 10% of me wanted to complete our grand slam earlier than June!)