Full backups are created too often

I'm backing up to Rackspace with ~53 GB (uncompressed) dataset. Because my machine is a laptop that isn't always on, and because DD apparently uses bandwidth sparingly, a full backup takes considerably more than a week to complete. Then, it only does very few incremental backups before it decides to do another full backup. The upshot of this is that there's a full backup running on my machine nearly all the time.

My backups are scheduled to run daily, and DD is configured to keep backups for at least a month.

Requested info:

1. I don't know how to get a log file, since backups only occur when DéjàDup decides they should run, not when I want them to run.

2. deja-dup 18.1.1-0ubuntu1.1 duplicity 0.6.13-0ubuntu1

3. deja-dup settings:
org.gnome.DejaDup backend 'rackspace'
org.gnome.DejaDup delete-after 28
org.gnome.DejaDup encrypt true
org.gnome.DejaDup exclude-list ['$TRASH', '$DOWNLOAD', '/home/scott/.VirtualBox', '/home/scott/bin/install', '/home/scott/Dropbox', '/home/scott/dropbox_backup', '/home/scott/.Skype', '/home/scott/.Skype.bak', '/home/scott/Church/MAP Seminar']
org.gnome.DejaDup include-list ['$HOME']
org.gnome.DejaDup last-run '2011-08-09T16:28:15.067732Z'
org.gnome.DejaDup periodic true
org.gnome.DejaDup periodic-period 1
org.gnome.DejaDup root-prompt true
org.gnome.DejaDup.File icon ''
org.gnome.DejaDup.File name ''
org.gnome.DejaDup.File path ''
org.gnome.DejaDup.File relpath @ay []
org.gnome.DejaDup.File short-name ''
org.gnome.DejaDup.File type 'normal'
org.gnome.DejaDup.File uuid ''
org.gnome.DejaDup.Rackspace container 'redacted'
org.gnome.DejaDup.Rackspace username 'redacted'
org.gnome.DejaDup.S3 bucket ''
org.gnome.DejaDup.S3 folder 'redacted'
org.gnome.DejaDup.S3 id ''
org.gnome.DejaDup.U1 folder '/deja-dup/$HOSTNAME'

4. Ubuntu 11.04