Best way to delay a rule so a folder is 'filled'

I have several rules set up that take a downloaded folder copy the folder and contents to a temp folder. Then I move these folders to a NAS directory for import into iTunes. Trouble starts if the first rule executes before the folder is filled with the download.

Match All:
Subfolder Depth > 0
Date Last Modified is not in the last 2 hours
Kind is music
Extension does not contain part

Do following:
Run Applescript embedded script (that found on this forum)
Copy file to folder Music Downloads
Set color label red

It works great except for the simple timing issue. What is the best way to delay the execution of the rule, or look within the folder to check that it is filled with files that have completely downloaded (not .part)?

Thanks jm

The folder modification date is only updated when the file is added, not when the files in them are finished. What program is doing the downloading?

Thanks for the reply.

Transmission is doing the downloading. I am trying to find a way to either wait long enough or maybe move files as they are completed. Duplicates are the problem as I can't figure a way to purge the files that are processed. I am stubborn so I will find some work around.

Transmission has an option to use a different folder for incomplete downloads. If you do that, have Hazel monitor the folder with the complete downloads. I believe that should solve your problem.