diff --git a/README.md b/README.md
index 5618a53..4cdf88a 100644
--- a/README.md
+++ b/README.md
@@ -174,6 +174,41 @@ Just dive in and copy the files out of the snapshot:
     cd /backup/hosts/example.com/.zfs/snapshot/ && \
     rsync -aH --numeric-ids 2012-11-04-15:40:49-1352004049/d/ example.com:/restore-point/
 
+
+## Retention Policies
+
+Each backup has a TTL defined, after which the prune script will delete the 
+backup's snapshot. You can configure the retention/expiry of backups through 
+various configuration properties. Each of them defines the TTL by means of "fully days after 
+backup creation". A value of 0 defines "keep forever".
+
+Once a backup is created you can't change the TTL anymore, as it is stored 
+within the read-only snapshot.
+
+A specific expiry TTL given as last parameter to the backup script 
+overrules any of the other TTL configuration.
+
+The default TTL configuration is set in the required property ``EXPIRY``. It gets
+applied when none of the other option matches.
+
+All other options apply until to the first complete/successful backup at a given day:
+
+* ``EXPIRY_DAY``: TTL for daily backups
+* ``EXPIRY_WEEK``: TTL for the backup on a Monday
+* ``EXPIRY_MONTH``: TTL for backup on the first day of a month
+* ``EXPIRY_QUARTER``: TTL for backup on the first day of a quarter
+* ``EXPIRY_YEAR``: TTL: for backup on the first day of a year
+
+If a given day matches multiple conditions, the expiry configuration for the longest 
+period that has a non-empty value gets selected. E.g when on January 1st ``EXPIRY_YEAR`` 
+is not set, but ``EXPIRY_QUARTER`` and ``EXPIRY_DAY`` are, then 
+EXPRIY_QUARTER gets selected.
+
+When a backup doesn't succeed completely (partial backups), then the configured TTL 
+gets also applied to the next attempt to do a backup at the same day. If all backups 
+at a given day (partially) fail, then you won't get a backup with the special TTL. 
+You then would have to trigger a manual backup with a TTL set explicitly.
+
 ## Status
 
 This has been in production use for many years now and is stable.
diff --git a/bin/backup.sh b/bin/backup.sh
index 204acda..957a06a 100755
--- a/bin/backup.sh
+++ b/bin/backup.sh
@@ -70,7 +70,23 @@ fi
 sourceHostConfig $HOSTS_DIR $HOST
 
 # Options Overridable by backup.conf (or command line)
-EXPIRY=$(expr ${3-$EXPIRY} \* 24 \* 60 \* 60 + `date +%s`) # Convert expiry to unix epoc
+
+if [ -z "${3}" ]; then
+	NUM_BACKUPS_TODAY=$(find ${HOSTS_DIR}${HOST}/.${POOL_TYPE}/snapshot -maxdepth 1 -mindepth 1 -name "@$(date +%F)*" | grep -v -e "-partial$" | wc -l)
+	if [ "${NUM_BACKUPS_TODAY}" -eq "0" ]; then
+		if [ -n "${EXPIRY_DAY}" ]; then EXPIRY=${EXPIRY_DAY}; fi
+		if [ -n "${EXPIRY_WEEK}" -a "$(date +%u)" == "1" ]; then EXPIRY=${EXPIRY_WEEK}; fi
+		if [ -n "${EXPIRY_MONTH}" -a "$(date +%-d)" == "1" ]; then EXPIRY=${EXPIRY_MONTH}; fi
+		if [ -n "${EXPIRY_QUARTER}" -a "$(date +%-d)" == "1" -a "$(expr $(date '+%-m') % 3)" == "1" ]; then EXPIRY=${EXPIRY_QUARTER}; fi
+		if [ -n "${EXPIRY_YEAR}" -a "$(date +%-j)" == "1" ]; then EXPIRY=${EXPIRY_YEAR}; fi
+	fi
+else
+	EXPIRY=${3}
+fi
+
+if [ "${EXPIRY}" -gt "0" ]; then
+	EXPIRY=$(expr ${EXPIRY} \* 24 \* 60 \* 60 + `date +%s`) # Convert expiry to unix epoc
+fi
 
 # Check to see if the host backup is disabled.
 if [ "${DISABLED}" == "true" ] && [ -z "$FORCE" ];  then
@@ -99,7 +115,10 @@ fi
 (
 rm -f ${LOGFILE} # delete logfile from host dir before we begin.
 echo "inprogress" > $STATUSFILE
-echo $EXPIRY > ${HOSTS_DIR}${HOST}/c/EXPIRY
+rm -f ${HOSTS_DIR}${HOST}/c/EXPIRY
+if [ "${EXPIRY}" -gt "0" ]; then
+	echo $EXPIRY > ${HOSTS_DIR}${HOST}/c/EXPIRY
+fi
 echo $ANNOTATION > ${HOSTS_DIR}${HOST}/c/ANNOTATION
 
 STARTTIME=$(date +%s)
diff --git a/bin/list-backups.sh b/bin/list-backups.sh
index 6ac0811..c4e2f30 100755
--- a/bin/list-backups.sh
+++ b/bin/list-backups.sh
@@ -5,7 +5,7 @@
 CWD="$(dirname $0)/"
 
 # Source Config
-. ${CWD}../etc/backup.conf
+. ${CWD}../etc/backup.conf 
 
 # Source Functions
 . ${CWD}functions.sh;
@@ -35,7 +35,7 @@ for host in $HOSTS; do
             EXPIRY=$(cat $snapshot/c/EXPIRY 2> /dev/null)
             ANNOTATION=$(cat $snapshot/c/ANNOTATION 2> /dev/null)
             STATUS=$(cat $snapshot/l/STATUS 2> /dev/null)
-            echo "$host $SNAPSHOT $EXPIRY $STATUS \"$ANNOTATION\""
+            echo "$host $SNAPSHOT ${EXPIRY:-0} $STATUS \"$ANNOTATION\""
         done
     fi
 done
diff --git a/etc/backup.conf b/etc/backup.conf
index f3baa52..2779da7 100644
--- a/etc/backup.conf
+++ b/etc/backup.conf
@@ -9,7 +9,12 @@ RSYNC_ARGS='-a --numeric-ids --hard-links --compress --delete-after --delete-exc
 SSH_USER='root'
 EXCLUDE='/dev /proc /sys /tmp /var/tmp /var/run /selinux /cgroups lost+found'
 BACKUP_PATHS='/'
-EXPIRY='28' # Default backup expiry (in days)
+EXPIRY=7								# Default backup expiry (in days)
+EXPIRY_DAY=$(expr 7 \* 8) 				# 8 weeks (~2 month)
+EXPIRY_WEEK=$(expr 7 \* 25) 			# twenty-five weeks (~6 month)
+EXPIRY_MONTH=$(expr 2 \* 365) 			# two years
+EXPIRY_QUARTER=$(expr 5 \* 365) 		# five years
+EXPIRY_YEAR=0 							# unlimited
 SSH_KEY=~root/.ssh/id_rsa.pub 
 SNAPSHOT_ON_ERROR=false  # Snapshot after rsync errors
 PRUNE=true  # Prune old expired backup snapshots