Its good to fly with different instructors. Most of us use a practice
called "off-winging". Its a military term (I'm told). It basiclly means
you send your students to fly with another CFI every once in awhile. It
makes a **HUGE** difference when checkride time comes. If you've only
flown with one CFI the existance of a strange examiner in the plane
with you is just one more source of stress.

-Robert, CFI