expo is good for umm 3 things, or there about...
old flyers with shaky hands, sorry but its true
low flying where you need to control the pitch very carefully
to control a over controlable plane.

for the last one i have a Outlaw, its rolls are the quickest i've ever seen, most of the time i stay within the -60% expo ( use just the middle of the sticks range). then when i want to spin or flip i'll wack it over right out of that range.
however, this leads to a bad suituation if you suddenly have to react because you'll auttomaticly come out of the expo and get in more trouble... done it a few times with this plane.

-60% is far to much for any non 3D/mental plane.
for trainers upto -20 on the elevator can help with smoother landings, but it all depends on the pilot and plane, do what feels right to you.