Moving Emails into New Folders

Hi, 

I'm looking to clean up some of my email campaign folders. We currently have our system structed as following:

YEAR > EVENT 

Some of these event folders are becoming overwhelmed, so I would like to break it down farther with additional folders to organize the emails already in each event folder. Such as:

YEAR > EVENT > LOGISTICS
or
YEAR > EVENT > MERCHANDISE 
or 
YEAR > EVENT > NEWSLETTERS

Will I run into any problems moving emails that already complete?

Thanks, 
Stephanie