Keep them. Send them to someone you like, preferably someone with the same taste in music. Or send them to someone you don’t like and that you know hate your taste in music. It’s a very cost effective revenge, it’s only a mailbox away and, as someone once said: revenge is a dish best served with a stamp on it. Nah, no one ever said that, to our knowledge. But hey, you can write that on the back of the card!