systemd journal using too much disc space

[Colin Law]

I note that the files in /var/log/journal are consuming 2.9GB and
journalctl --disk-usage
also shows 2.9GB. Since this is on Ubuntu 17.04 installed in an 80GB
partition on an SSD this is a significant chunk of my free disc space.
As far as I can see journalctl is using its default values as there
are no commented out settings in /etc/systemd/journald.conf and I
cannot see any overriding conf files.

I see how to adjust the settings for this but am surprised the default
is so large. For example if I run
journalctl -u systemd-resolved.service
I see 70,000 lines going back over 9 months which seems a bit excessive.

Is what I am seeing to be expected for the default settings?

Colin