[plug] Q for the spamassassin experts?

[W.Kenworthy]

I am running spamassassin on my home mail server - works reasonably
well, but lately there has been some 'leakage'

I collect mail from iinet via fetchmail - it has been premarked by
iinets email scanner, which appears better than spamassassin, though
often one will get something the other misses.  Very few to almost nil
false positives from either!  spamassassin looks like it ignores iinets
classification marks and does its own checking.  I am not current using
iinets checks, except to keep tabs on spamassassin.

My question(s) are on training spamassassin:

1. currently I am only moving 'likely-spam' to the training directory:
should I be moving everything, including those classified as spam?

2. How many messages do I keep in the training directory: 3 months worth
(to track the spam profiles as they change, so older spam 'drops out' of
the training set), or everything forever?  Processing time for training
on the 1Ghz P3 on which the mail system runs is starting to get
significant which is why I am looking at this!

BillK