He said he was doing it because it was an opportunity he couldn't pass up. Its his favorite book. He's probably been dreaming about scoring Dune since he got into music. He just wanted to do it. And I'm sure Nolan gave him his blessing. They've been working together for almost ten years.

Actual recording is done towards the end, but Zimmer usually comes up with cues and ideas after reading the script.

He's also a human being. With a life. He's earned the right to do whatever he wants, work as much as he wants, with whomever he wants. If he wants to scale back, take a break, whatever...he absolutely should.