I have always be somewhat uncomfortable with the notion of “repurposing”. It's like leftovers. Nothing wrong with it. But not quite the sort of thing to serve dinner guests.
To repurpose is to re-use an existing product with minimal modifications so as to create a brand new product. Old copy re-released as a brand new book is not exactly "new" is it?
We can't possibly invent brand new material from scratch every time of course. We can leverage past work without making it a cynical marketing exercise.
I prefer the idea of "purposing."
To "purpose" existing material is to tailor existing concepts and material to suit a specific audience. Not so much copy and paste as understand the audience, reread the existing material, reconsider it in light of the audience, and rewrite/tailor it to suit. All in all a far more respectful exercise don't you think?
Image: Leftovers via Shutterstock.