Thanks for the info. I did cancel the mirror. still, it looks like old.zip is
being deleted with each update (so that new.zip can be renamed to old.zip). it
also looks like new.zip only contains the files updated in the last update, so
these would be the only ones kept when old.zip is deleted. is this because the
mirror was cancelled? or is there some other reason for discarding the cached
files?
the timestamps on this particular server are correct. the files in question
have timestamps around  Jan. 2007, so there's no reason they should be
downloaded again.