Set keep=8 in the weekly cron job.

dajhorn · dajhorn · commit d99147db7aed · 2011-12-21T20:29:27.000-06:00
A default of keep=8 for weekly snapshot is more useful than keep=4,
which is no more protective than the default daily schedule.
diff --git a/etc/zfs-auto-snapshot.cron.weekly b/etc/zfs-auto-snapshot.cron.weekly
@@ -1,2 +1,2 @@
 #!/bin/sh
-exec zfs-auto-snapshot --quiet --syslog --label=weekly --keep=4 //
+exec zfs-auto-snapshot --quiet --syslog --label=weekly --keep=8 //

Original file line number	Diff line number	Diff line change
`@@ -1,2 +1,2 @@`
`1`	`1`	`#!/bin/sh`
`2`		`-exec zfs-auto-snapshot --quiet --syslog --label=weekly --keep=4 //`
	`2`	`+exec zfs-auto-snapshot --quiet --syslog --label=weekly --keep=8 //`