Continuing the "this might sound silly"-theme:
Why not use cron to rotate the greylist.conf and restart the milter?
(will HUP be enough? I don't know).
(Remember to use different dump files, unless you want the greylisting
from the night to affect the day and vice versa.)
That way you can greylist special (unfriendly) networks, etc. also at
work time.
ElrondMessage
Re: Time-based greylisting?
2005-05-27 by Elrond