I have no idea what to do with cards.

I received several for my birthday and I was trying to figure out what to do with them when I realized I still have cards hanging around from last year. Is there a time period for keeping cards? Is it like keeping pay stubs or receipts? Right now I have them all in a drawer by my bed. I really appreciate the cards but there has to be a card keeping time limit. Am I alone on this? Who is with me?