I got multiple 48 Hour Xbox live cards from my blockbuster and then I have a 1 month card. I also currently have one month that ends in 3 weeks. If I go ahead and redeem all the codes will it just keep stacking up? or will it use the last one entered?

they should stack. i seem to remember getting a 1 month card with my xbl camera and being able to add it to my current subscription.