Yes, you can... but I believe I read an issue someone on here has recently..she booked her reservations and had to cancel it. They wanted to refund it back to the cards she used, but she had thrown them away.... It ended up working out in the end, but seemed very frustrating for her! I would absolutly keep the cards until you go, just incase something like that comes up. Even if you dont want to keep the actual card, you could probably make a photocopy with several to a page, just as long as you have the #'s.
HTH