running texpire weekly instead of daily?

I have a fairly long retention period in my leafnode configuration,
and the cron.daily/leafnode job takes about 1 hour to run.  (I'm
running leafnode-2.0.0.alpha20110807b.luascript, and the cron script
might have been copied from an old Debian/Ubuntu package.)

Is the texpire running time related more to the size of the spool or
the number of articles that it decides to delete?

Would it do any harm to run it weekly instead of daily?

Thanks,
Adam