Forget the empty platitudes; your star employee is not a "godsend." They are a person deserving of your not infrequent acknowledgment and worthy of appreciation and respect. When was the last time you thanked them -- really thanked them?
In my line of work, I frequently communicate with CEOs and their executive assistants, and nowhere is the need for gratitude more clear.
After one CEO's assistant had been particularly helpful, I replied to her email with a grateful, "I hope your company and your boss know and let you know how valuable and special you are."
She emailed back, "You don't know how much your email meant to me." It made me wonder -- when was the last time her boss had thanked her?