Steve,
I wanted fade in, keep the butterfly effect going for a while, then fade out. I tried using a single effect, but it did not give the desired effect. So, on one line I put three butterfly effects, adjusted their time lines so that the motion was continuous (no jumps), then used the 1st one to fade in and the last one to fade out. If this can be done using a single effect, I couldn't get it to work for some reason. I will keep plugging away at it, but for now, I have what I was looking for.
Thanks