I don't play the slots. I did see several people hit on the slots, but also heard many of the people say they lost money. So I really can't help you much there. The Casino was open very late (at least to 1am) but there was a night were there just wasn't that many people gambling and they shut down most of the tables early. On the Dream, on days we were not in port in the morning, the slots were open 24hrs.
And stay away from the Bingo. They sell you an electronic bingo machine that has like 18 cards on it for about $60. But you don't know what the prizes are going to be until after you start playing! The one and only Bingo game I played they had a special going and I got to play for $45, but the first prize was $60 and the highest of the 5 games played paid out $120. Not really worth gambling at those rates.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007