Bayes expire files

[Julien Gormotte]

Hello everyone,

I have a problem since some time (I don't know exactly when it began) :
spamassassin has lots of bayes_toks.expirexxxx. I had no such files in
august (I have a backup of this time period), so it seems new...

The problem may come from a recent update, as I update my system pretty
often. I did not changed a lot of things on this mail server, and I
don't think I touched amavis config...

It became problematic when I got an alarm because my filesystem was
full : these files took more than 35 GB...

So, anyone knows how to get rid of these ? Is that a new feature ?
What are those files ?

I'm running amavisd-new-2.7.0 on FreeBSD 8.2, with package
p5-Mail-SpamAssassin-3.3.2_2 (and a few others).