Well ... it's not genius. It's like one of those sketchy home maker tips you see in New Idea when you're in a waiting room and all they have is a woman's mag so ancient that Princess Di is still alive in their world.
Anyway ... and I am sure that others have thought of this ... cards. The problem with cards is they're expensive for what they do. They're like $5 and a one use. They sit around for a week or so in victorious celebration or commiseration of an event whose import eventually fades into the dust of time. Then the card gets chucked.
So ... a solution! Write your message to the person or people in question on a post it note. That way when their date has time faded they can yank your sticky missive from the middle and re-use the card on another person.
Hah! Of course the people at Planet Ark won't like that and will probably send retired tennis players to beat me up. But I will not be silenced!