So I think this must be a configuration issue on my part... I checked another AS 6 server and its log files were rolling over correctly. Now I see that the logs on the server that I thought was not rolling over have since rolled over, but not at midnight (they rolled over a little past 10AM local time). So this makes me think I've got some time zone issue or something going on and not a real issue with AS 6 logging.
If I figure out what my issue is I'll post back.