No expo can be manageable if you have very low rates.

I know a very good 3der who only uses about 20% expo on high rate all the time, but he has very very high resolution thumbs.

So having said that i think it really depends on your flying style. If its fast and dramatic with lots of flicks and sharp point rolls (so with the stick halfway bettween center and maximum travel for a lot of the time) and so on then i think you dont need so much expo. If its smooth stuff with some contrastingly violent 3d thrown in then now and then then you'd use more expo.

I personally use about 40% expo on low rate for all three surfaces, 60% on middle rate and 80% on high rate- basically so that the plane feels almost the same with the stick close to the centre in low, middle, and high rate. I have both expo and throw all on one triple rate switch, so it basically acts like a flying style switch.