New Post: Copy Worksheet is very very slow

I can't get past the fact that either way you end up with a huge file you need to save, what happens before shouldn't be an issue (you still need to save it). In the case where you copy the 200 sheets into a single file you still have a big file that needs to be saved, just as if you wrote the file in one shot.

Are you sure you're disposing objects when you write everything to it?