True, the reload time is not documented as far as I know.
It will be added to the FAQ.
With the mirror settings,
the second FAQ point for a local site is
closer to what you want. If the site you list first
isn't found, it will fall back to the second site.
Which means you could probably get what you want by
listing your local archive as the second site on your
list.
But I see you have sent mail to the list, which is
probably best for discussing features in detail (I
just include this reply for anyone else reading the
thread).