[MacDV] Render files - Clean out

[KS]

As a newer user of FCE, I'm wondering if I can delete all the extra  
Render files I find scattered in different locations
on my external drives.   Once I complete a specific project – if I  
trash the render files related to that project – will I be able to  
revise/update the video at a later date?

I don't see that issue addressed in Tom Wolsky's book – although  
maybe I've missed something.

Thanks for any help.

ks