since no-one answered for serveral hours forgive me for having a go.
1) can you state if your printer is serial or usb etc please?
In other words if cups is running (or should be running) it it useless with the usb udev stuff.
2) you also mention that cups is module...and I am wondering if your kernel is unloading the module after boot up...so your syslog may show cups and then due to inactivity...it unloads
And that would not cause me any concern unless you insert printer cable and the thing does not print.
But I am guessing you leave your usb cable in all the time? can you confirm that is the reason why you are issueing the restart command?
3) to save further questions...maybe from others could you reboot your computer and
lsusb > /home/yourname/lsusbboottime
lsmod > /home/yourname/lsmodboottime
...pull out usb printer
redo above commands and only keep a copy if they differ
also keep a snip of your /var/log/syslog from boottime to end of printing (or fail etc)
then post them to http://paste.debian.net/
good for 72 hours or your online sharing site etc.
4) Altho it may be un-related...could you confirm if you have recently created etc any udev rules for any usb device no matter how unrelated pls.
and I assume your printer works in BSD?