For the project I am currently working on, I can either
A)Make a symbol containing 100 frames. The frames consist of 5 different animated setups that run for 20 frames. I can add a child instance of this 100 frame symbol on a particular frame and then remove it after 20 frames.
B)I can make 5 different symbols, each one only containing the 20 frame animtion, removing the child when the animation stops.
The animations are triggered by game scoring, so I am wondering if constantly adding the larger symbol to the stage will make a difference in terms of efficiency, or if only the number of frames being played matters?
I don't think that it will make any difference at all. As an alternative, you can just move that symbol into the visible area of the stage when you want to use it and then move it out when you are finished with it.
You could also make the 5 different animations in their own movieClips, then place those in a "holder" movieClip.
That way you can place that on the stage and switch animations easily by using the "graphic / single frame / #number of the frame - animation you need" setting.
That's how i would do it.