One way that I re-use cards from my huge collection is to put one from the drawer on the shelf when I put fresh flowers out - I look for one which suits the flowers - in this case the card has both the colour of the vase and of the flowers....
..and a whimsical message which makes me smile.
I get to enjoy them all over again!
(But I will reduce the number a bit, and remember that I don't expect anyone who gets a card from me to keep it forever, and that no-one's going to be upset if I recycle their card!)