How do I know when to much expo is dialed in?

When your reaction over-corrects. About 25% for me.

I see.  Thank you.

Depends on what kind of plane and what kind of flying you're doing. Then it moves on to personal feel. I like crisp controls because I'm used to it from flying helicopters, some airplane only guys think my planes are too sensitive. I've flown theirs and think they are too mushy.