An interesting [discussion on the Sandvox Yahoo! Group] from problems Publishing a site lead to the idea of publishing to the local Sites folder in the Home directory. This way, any changes in Sandvox could be published locally without having to export the whole site. This locally published site would leave the creation dates of older files unchanged. The advantage of this is that when synchronising the local folder with the server using an FTP client, the unchanged local files will be the same creation date as on the server. When exporting a site from Sandvox, all files are given the creation date and time of export. This means that all local files are newer than the servers files and synchronising with an FTP client will upload the whole site.

The how to instruction is here: [Sandvox - Setup Host to Publish to Local Folder]