Bayesian database not learning

[Douglas Ward]

I trained my bayesian database about four weeks ago with about 600 or
so ham and spam messages.  Spamassassin should be autolearning based
on the following defaults:

bayes_auto_learn_threshold_nonspam 0.1
bayes_auto_learn_threshold_spam 12.0

In the four weeks since I trained the database it does not look like
it has learned anything.  When I run the sa-learn command the spam/ham
count is the same as the day I trained it.  Are these defaults to
high/low?  Should they be changed?