I am thinking of planning my first cruise as an adult and I just noticed that my Discover IT card rewards offers gift cards to various cruise lines that will double my money. I can use $30 to get $60 or use $60 to get $120 and there isn't a limit so I figure I could use a bunch of them to basically get my cruise for ~50% off.

This seems like an amazing deal, but since I haven't been on a cruise since high school and I'm new to planning it by myself, I wanted to check to be sure there's not something I'm overlooking. Do you guys recommend this? The companies offered are: Carnival, NCL, RCL, Celebrity, and Princess.

Thanks in advance!

Edit: Looks like I jumped the gun. You CAN buy as many as you want, but can only use one per stateroom. Bummer.