I have some newsgroups with very large expiration times, because
Yarn gives me more capability with newsgroups than with folders.
Perversely, Yarn seems to stick messages from these groups at the
end of the news.dat file. I don't WANT to delete these messages --
so 'rebuild' is my only choice to reclaim space in news.dat. [And
you can imagine how pleased I was when 'rebuild' TOTALLY WIPED OUT
a pseudo-newsgroup for which I had unwarily specified keep=9999.]
mikus