@luckman212
I use a manually added FreeBSD package, 'munin' that came with a file to be placed in /usr/local/etc/rc.d/
As per pfSense needs, I renamed it - added the .sh extension, and now the munin process get started at boot, and stopped at shutdown.
I made this install many years ago, and as far as I know, the script only executes during boot and system shutdown.
Not for network or other events etc.
If FreeBSD would look like a Debian system (or clone) using init or systemd I could tell you way more, and I even think pfSEnse isn'tv really FreeBSD (no surprise, at it is, and it isn't ^^).
Look at the kea script for an example, the first 3 / 4 lines.
Afaik, pfSense it self, see here /etc/, all de rc...... files - for example rc.bootup - will all all these files.
pfSense handle the hardware and software system events, and call whatever is needed, if system processes like 'unbound' needed to be restarted.
So :
and also during certain system events (e.g. interface link changes, IP address changes, and gateway events).
never saw that happening with my own processes - as pfSense isn't really aware that these are running ones the system is up.