Why does it need to run 5 times? If you've got 5 people with different settings, you can run spamassassin one time and still have individual preferences. The score of a message is not determined by a user's SA preferences in most cases.
Indeed, few people change the list of tests to be performed or the scores of the individual tests; but now that SA has Baysean filtering it is quite simple for individuals to maintain their own training sets to define what they do or do not consider to be spam. And that will lead to different scores for the same message.
I know this is fairly easy to do in Exim. (Using SA from a router rather than an ACL.) I suspect it's not too difficult for other MTAs. (It does prevent the use of Cyrus' single store option though.)
-Pat
