Just as an example... I usually like to keep the Front/ Three Quarter/ Side in one symbol (head symbol). And the mouth in another. I use a blank layer to label the views. To enhance the animation I like to sync jaw movements and the mouth accordingly. Some times due to the amount of lipsync assets I have it exceeds 100 frames. Is there a way to extend that?
Here are pictures that showcase how I setup the head just in case.
(Note: the link I posted is just to illustrate how I set it up. These do not exceed 100 frames but projects that I have that are setup in this manner do)