David - good post. It may be that another hour or so of circuits is just the final hurdle to jump through before you can start doing more interesting flying, and *really* start learning! I'd suggest taking him up on it, making sure you have a full discussion and briefing before the flight about what he thinks you need to cover, and how you're going to cover it. Then you can concentrate on skills while in the air, doubtless gain some valuable knowledge, and get off on your own forthwith!
It'll be worth it - I tend to regard that any dual training is good dual training!