What are your thoughts on routine in the music practice room or the actual lesson?

In the music lesson I have found some students seem to really love routine and are actually thrown when things are done in a different order. Whereas others respond much better to a more spontaneous approach (or at least something that seems spontaneous – even though we might have planned what we are going to teach beforehand!).

It seems to be very much a personal thing and differs from student to student.

What kind of lessons do you give? Is everything done in the same order every week, such as scales or technical work followed by repertoire? Or do you like to mix things up?