When I got my first radio that had expo I read what it did then asked my advanced instructor about it. I'll tell you what he told me and I have told my own students over time.
Go ahead and set your plane up with expo and see what it does and if you like it or not, it's not earth shaking, it just softens your controls or it can go the other way and make them more active around center. On an LT 40 it really makes no difference but it's a good plane to test it and see if you like it.
My planes are all stunt types and if I don't soften the controls you can see the planes moving from my shaky hands when I'm flying straight and level, you would never see it on a LT but you can on a pattern plane.
I start at about 35% then adjust depending on how sensitive a plane is.
I have always allowed my students to test these programs that the advanced radios have just so they know what they are and do. Flaperon is the one that always catches everyone's attention, it really got mine and I just had to give it a try. On some planes it's fun and on others it's a crash waiting to happen.
I did all my radio program testing on an Up-Roar fun fly plane over a period of time. An LT isn't the best test platform but it's a good one to see what expo does. Not needed but it will show you for future use.