Yes, as
@Marionnette, you just transfer the balance from one card to another. I've done it many, many times and in fact, I did it not 5 minutes ago.
You do not have to register each card though in order to transfer the funds. You only really need the one. When you go into the transfer option, it will list your registered cards and then says
OR
Enter Card Information
If you hit that blue button, you'll be asked to enter the account number and security code for the card you want to transfer the funds FROM, and you'll be able to select the registered card you want to transfer TO.
It's very simple.
Note, that an individual gift card can only have a max of $1000 on it. If you're going to do more than that, you'll need to put those additional funds on another card.
You really don't need to keep all those cards registered, one you've transferred the funds. You can remove them from your account.
That said, it's a good practice to have a second (empty) card on your account. Should you discover that you've lost your giftcard (or even if you *think* you have), it takes less than a minute to log in to your giftcard account and transfer all the funds from the list card to the other one.
I have 4 special cards that I've picked up over the years and those are the ones that stay in my account and that I always bring with me.
Steve