Making Timelines to Go into Frames

I am making a 50-frame my_movie.fla with several layers of buttons and graphics already in it. The movie plays manually (by button press). It is, in essence, a state diagram.

The graphics and buttons must be visible and accessible throughout the entire movie. Only one element changes depending upon which frame is current.

Some frames in my_movie will contain level 2 of the state diagram. Some of the level 2 frames will contain level 3, etc. I’m assuming these are all timelines.

Do I make the timelines as (A) individual *.fla files and point to them in Level 1 of my_movie or (B) do I make them as mc symbols and place them in the level 1 frames?

QUESTION 2: If (B), how do I make them - make them on a temporary new layer, make a symbol for each, then blow those frames away?

Any ideas are appreciated.