[O] How to specify APPT_WARNTIME for entire files?

[Jorge Morais Neto]

Hi.  I have set appt-message-warning-time to 10.  However, there are two
files where I would like the warning time to be 0.  Is there a quick way to
do it?  Which?  I do not want to add APPT_WARNTIME properties to each entry
because, if I did that, then:
1. Every time I added a new entry to one of the affected files, I would need
   to remember setting APPT_WARNTIME to the correct value.
2. To later change the warning time for the affected files, I would need to
   change APPT_WARNTIME in each of their entries.
3. There are many such entries, so it would be space-inefficient to have
   APPT_WARNTIME in each.

I have tried to specify "#+PROPERTY: APPT_WARNTIME 5" and enable inheritance
of it through org-use-property-inheritance, but it did not work.  I have
also searched the web and the Org mailing list archives.

I am using Org mode version
9.0.3 (9.0.3-elpaplus @ /home/jorge/.emacs.d/elpa/org-plus-contrib-20161224/)
on GNU Emacs
25.1.91.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.18.9) of 2016-12-31

Regards
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