I notice from my AWS usage numbers that there are about 6MB of PUT requests from W3 Total Cache every hour, which is generating some many hundreds of thousands of PUT requests each month for a low-traffic site. I imagine this is the plugin uploading all of my wp-content and wp-includes files every hour. When I look at the management console, all of the files do indeed have a timestamp of the last hour.
I notice that the "Auto upload interval" is set to 1 hour (3600), but it seems that uploads should only occur if files change. I'd be happy to increase that number, but I'm curious why the upload is happening at all when nothing has changed.