rsync transferring identical files

[Ben Pirt]

Hi all,
I have set up a backup system which is syncing files between a linux  
based file server and a remote server on the internet.
After doing an initial rsync with the following command:

rsync -a --delete --numeric-ids --relative --delete-excluded     -- 
exclude=*__software* --exclude=*.AppleDB* --exclude=*.DS_Store*     -- 
exclude=*:2e* --exclude=*.AppleDesktop* --exclude=*.AppleDouble*    -- 
rsh=/usr/bin/ssh backup at myserver.com:/storage/files     /backup/ 
location/

and letting the process run for about 5 days, I changed a few of the  
files and ran it again and now it seems to be transferring all of the  
files again, even the ones that haven't been changed. The servers are  
in different timezones, but from what I have read this shouldn't  
matter. If I run the command again and let it transfer a few files,  
then stop it and run it again - it seems to "fix" the problem for  
those files, even though they have identical timestamps and sizes as  
before.

Is there anything I can do to avoid having to run this again for a week?

All the best,

Ben