Akismet problem?

This may seem a weird thing to question, but after weeks of madly catching all kinds of spam on a daily basis, suddenly Akismet has stopped no spam for a week. Zero. There haven’t been any spam comments that have gotten through, either, so it’s not like it isn’t stopping spam.

I do not have “Automatically discard spam comments on posts older than a month” checked.

I’m using WordPress 2.2.1.

Nobody has reported problems leaving comments.

The only thing I’ve done “new” recently is to turn on wp-cache. But I continued to receive spam for several days after that.

I’ve been getting spammed daily for three years, so it seems hard to believe that the spammers have suddenly given up.

Should I be worried about this? Or just enjoy it?