Ah yes, I realise that rsync does delta changes hence why I'm using it, but, we don't have enough disk space at the remote sites to store everything.
My plan is to:
1. Use find -atime to generate a list of files accessed over 30 days ago to exclude from the rsync process
2. Rsync to the remote site using the exclude list
3. Use find -atime and -exec to bin files accessed over 30 days ago at the remote site
4. Bin any empty directories at the remote site