FCP7 workflow for feature film - nested sequences and render issues

I am finishing off my first film. And each scene is its own sequence. Depending on the scene, it may have further nested sequences.

I created a master film sequence and dragged each scene into it.
So I have a series of nested sequences.

However, I find that I have to do multiple renders. So if I render the bottom sequence first, I still have to render in the master film sequence.

I am now trying an alternative with exporting to a QT ref file and bringing it into the master film sequence. This saves on rendering, however I am wondering what happens if I change the sequence that was render as a qt ref.

Do I need to re-export a qt ref file and re-import into the master film sequence ?