Do any Amazon S3 clients allow automation for setting expiration headers? I am using Transmit and the Firefox extension S3 Organiser.   Neither completely satisfies my requirements  as both tools lack the ability to set an expiration header.  

This makes me cry, as I need to manually run a script to download files to a local machine, use an S3 API to set the expiration header, then upload the files back to the S3 server.  This is time consuming.

Does anyone know of a tool or client for Mac that allows the user to specify an expiration header?
I'm not 100% sure if it meets your needs, but Cyberduck allows you to set the Cache-Control header. See this link for more information (see the section on Cache Control Setting).