from what i have read on "ask Audyssey", it's always better to take 32 readings if your version will accept it, although there are restrictions as to where you may take the readings.
if you haven't done so, you should read this carefully, a required reading:
http://www.avsforum.com/avs-vb/showthread.php?p=14456895#post14456895

See: http://www.blu-ray.com/community/gallery.php?member=Gelli
or: Axiom Gallery