NOW you're opening a can of worms [8D]

Some. Depends on the pilot and how "hot" of a set up. generally speaking the more throw you have to use for your pattern, the more expo you're likely to use to make it less sensitive around neutral.

Goofing around with a lot of "top" pilots, some use a good bit and some use very little, if any. There's no correlation between the amount of expo and the skill of the pilot, it's a personal thing.

Set the plane up to have enough throw for your manuevers, but not much more. It's ok to have a little extra in reserve, but don't have it at 25 degrees of travel when you only use 12 to fly your pattern.

After you have your throws dialed in, then crank in some expo (to be softer around center) to feel. Too much and it's like flying a sluggy pig, and too little and hitting your marks smoothly becomes very difficult.

-Mike