CUPS logrotate is configured in /etc/logrotate.d/cups-daemon. By default, logrotate is performed daily, and after the rotate CUPS is restarted.

/etc/logrotate.d/cups-daemon

/var/log/cups/*log {
        daily
        missingok
        rotate 7
        sharedscripts
        postrotate
                invoke-rc.d --quiet cups restart > /dev/null
        endscript
        compress
        delaycompress
        notifempty
        create
}

By default, the installation of logrotate creates a crontab file inside /etc/cron.daily named logrotate. As it is the case with the other crontab files inside this directory, it will be executed daily starting at 6:25 am if anacron is not installed. Otherwise, the execution will begin around 7:35 am. To verify, watch for the line containing cron.daily in either /etc/crontab or /etc/anacrontab.

How does this happen?

Taking Ubuntu 16.04 defaults as example:

/etc/crontab

...
25 6	* * *	root	test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )
...

If anacron exists, test -x /usr/sbin/anacron will return true, and prevent the second half of that line from running: in that case /etc/cron.d/anacron must be edited to change daily scheduled time, since that's the config that will kick off anacron itself.

/etc/cron.d/anacron

30 7    * * *   root	test -x /etc/init.d/anacron && /usr/sbin/invoke-rc.d anacron start >/dev/null

anacron is started at 7:30 am, but hang on … the actual anacron behavior is configured in /etc/anacrontab

/etc/anacrontab

...
# These replace cron's entries
# 1 = daily, 5 = number of minutes anacron waits, before executing the job.
1	5	cron.daily	run-parts --report /etc/cron.daily
...

So, effectively, CUPS daily logrotate is kicked off at 7:30 am by anacron, but the actual rotate is executed after a 5 minutes wait, at 7:35 am ¹⁾.

sudo vi /etc/cron.d/anacron

… and change line like this:

30 6    * * *   root	test -x /etc/init.d/anacron && /usr/sbin/invoke-rc.d anacron start 

man logrotate

sudo vi /etc/logrotate.d/cups-daemon
# change daily to weekly, monthly, yearly