Congratulations on an excellent image. Since the cats own the house and they're just letting you live with them they probably think they are just training you in this useful new skill of cat toy assembly. Just like parents with a baby's first steps they are justifiably proud that you have shown your first useful talent. After all, cats can only watch you pay bills, wash dishes, or sweep so long before becoming bored. If you were to leave the tree up year round Im sure the newness would wear off and they would leave it alone.