Once you upgrade all you need to do is make sure you're being notified of LTS releases only. You can do this by checking the file
# Default prompting behavior, valid options:
# never - Never check for a new release.
# normal - Check to see if a new release is available. If more than one new
# release is found, the release upgrader will attempt to upgrade to
# the release that immediately succeeds the currently-running
# lts - Check to see if a new LTS release is available. The upgrader
# will attempt to upgrade to the first LTS release available after
# the currently-running one. Note that this option should not be
# used if the currently-running release is not itself an LTS
# release, since in that case the upgrader won't be able to
# determine if a newer release is available.
Prompt= is set to
sudo apt-get dist-upgrade will never upgrade you to the newer release unless you manually change your
/etc/apt/sources.list or if you do a
do-release-upgrade, so you should be good to go.