Ninety second shutdown delay: "A stop job is running for system logging service"

I asked essentially the same question on the tde-devels list last week, and got this reply from a developer:

The 90s delays is the default timeout in systemd when somethings does not start/stop correctly… super annoying.
I usually edit the /etc/systemd/system.conf file and add these lines in:

DefaultTimeoutStartSec=5s
DefaultTimeoutStopSec=5s

This reduces the wait to 5s, which should be more than enough for any normal executing process to do what it needs.
I haven’t tried it yet, as I hadn’t run into one of these since asking the question until just minutes ago, but I’m currently trying to work out the cause ATM, which seems to be a bad NIC or motherboard going bad.