Yes punk head, all cards expire sometime, and if you asked that I will kick you in the ballsack and if you don't have one i'll hit you on your titties!
That would be up to the store that issued the gift card. Some gift cards do expire, others do not. It should say on the back or front of the card. If not, ask the store. Be aware of something else...
At least some iTunes gift cards has expiration dates. If you have a physical or electronical gift card bought from Apple or an Apple partner, it should be marked with expiration date if applicable....