A:AnswerIt just is a plastic card with the code. You need to purchase the card, but you can hand copy the code or type it and throw away the card, but if you copy it wrong or there is a technical support there could be a problem. It's best to keep the physical card until you have used the code online to activate the two months before discarding the card.
A:AnswerAs far as I know they have no expiration date in theory. I stopped playing for a couple of years and used one from two years ago and there was an issue with the code, but I spoke to a rep online about it and they fixed it without a problem or needing to go back to the store with a receipt. However if WoW stopped 2, 5 or 10 years from now, I can't guarantee that it would work under those circumstances.