I've started to make a lot of use of PhpED for SFTP. A real timesaver over the course of a day. But there's one headache - if I go too long without uploading, I get an error in the Transfers log:
Failed to check if folder "/path/I/am/uploading/to/" exists Socket Error # 10054 Connection reset by peer.

I guess the SSH session is timing out? Is there some way to prevent this?

It means that your server (remote peer in terms of connection) has closed connection.
To avoid it you may want to adjust sshd settings. Check if there is any timeout specified.
Additionally you may want to enable keep-alive for sshd and set its period to 1-2 minutes.

Thanks Dmitrie, that put me on the right path.