How do you know when they are ready ?

[tbavprof]

Talking to the examiners is good practice. I also used to do two debriefs with my students. One right after the checkride to catch the points that stuck out for them, and another a day or so later (when their adrenaline level is down and they've stopped staring and grinning at the temporary) to see if they actually remember anything else. Write these down and keep a book.

And Timza's point on the length is important...even more so with IR training, where once you done the basics, building up the stamina for an IR checkride is key.