Run plexupdate.sh on a schedule
This has been made very easy, just use the installer.sh found under extras/ and follow the steps. It will allow you to setup both a schedule and automatic updates.
Why should I use a config file?
Because putting your plexpass account information inside a script is a bad idea. Typically plexupdate.sh is run as root, which has a nice sideeffect, you can essentially make the plexupdate configuration file readable by you only or even just root, preventing other users to see your password.
Obviously, this might be a bit overdramatic since you're not likely running a multi-user setup at home, but in general, in the unix/linux community, placing ones credentials inside a script is frowned upon and makes it difficult to easily share the script since it now holds confidential information.
I want a per-user .plexupdate file back
If you desperately want the old behavior, please add the following to /etc/plexupdate.conf :
if [ -f ~/.plexupdate ]
source ~/.plexupdate
fi
This will make plexupdate.sh look in current user's home directory for configuration file. But this should be considered a stop-gap solution and is not officially endorsed.