Print jobs cancelled if waiting too long?
Printing in OS X is handled by CUPS, the Common Unix Printing System. Older versions of OS X had older versions of CUPS. A new It's not a bug, It's a "feature" was added in CUPS 1.6, which corresponds to Mac OS X 10.8 Mountain Lion, in order to prevent stuck jobs.

The MaxJobTime option, which defaults to 10800 seconds (3 Hours), will cancel the active print job on a printer that has timed out. The next job in the queue will start, either printing or eventually timing out.

From the cups.conf man page:


  MaxJobTime seconds
  Specifies  the  maximum time a job may take to print before it is canceled. The default is 10800 seconds (3 hours). Set to 0 to disable cancellation of "stuck" jobs.


Editing /etc/cups/cupsd.conf to include MaxJobTime 0 to disable this "Feature".

In my specific case, I used to be on 10.6.8 Snow Leopard until finally updating to 10.10 Mavericks, and wasn't aware of the change.