when to reload a zone with $include

[Gushi]

Hey all,

Here's the situation:

We're going to have at least part of our reverse DNS setup for a couple
of our zones generated by database (via a script I've written), but at
least part of the zonefile remains constant.

The plan was to just have the db-driven entries put into a separate
file, and then include that into the master zonefile.  This works well
enough, but I cannot figure out the answer to:

How can I communicate when this has been changed to the slaves (or the
master for that matter)?  I could in theory just keep running "zsu"
against the main zonefile, and keep forcing a retransfer (even as
slowly as once a day), but that seems wasteful.  I don't want to go the
length of making this a true dynamic zone, as these things are not
subject to change that often.

Running a DB-driven BIND is also overkill, we're not talking about
thousands of zones, just one.

Someone has to have come across this before.

-Dan