Thanks for the replies.
Particularly interested in the comment that if instructing then the student is flight crew (not pax, which makes sense) so the 90 day rule doesnt then apply.
So when I recently headed back with a student to avoid contravening the night requirement we could have continued for longer as there were no pax on board!
I'm a new instructor so I havent yet attended a seminar.......is the material that is discussed during the seminars available in the meantime? Seems a shame to wait for another two years or so to hear about these things!
Cheers