If the animation exists independently from the cam, there should be nothing more required than to extend it so it continues once the camera has come to a halt. Likewise, the camera would then only need an additional keyframe. It's really not clear what you are looking for or if there is anything specific in the project's structure that would prevent this....
The camera movement has finished at a certain point, at this point I want the composition containing the animating sphere/crystal ball to keep playing for longer than it already does (I need to make more of the end of the composition, I'm not sure how to do this).
The length of the composition is set using composition settings. Go to the menu bar and select Composition>Composition Settings.
You may also need to lengthen the layers. You can do this by clicking and dragging or by using the keyboard shortcut Alt/Option ]. If the footage is video and you have not trimmed the out point then other techniques will have to be used.
If this does not solve your problem I don't understand your question.
Thanks for your help guys!