Securing Local System, Password Expiration, Occasionally Connected MSDE

Numerous articles (e.g., http://www.microsoft.com/sql/techinfo/administration/2000/security/securingsqlserver.asp, even one that I wrote, http://www.dbazine.com/sql/sql-articles/cook12) state that to secure SQL Server, the SQL Server services should not run as Local System. That advice is useful only if making the change is not overly disruptive or is even allowable. My two most recent clients have absolutely rigid password expiration policies that require all account passwords to be changed at regular intervals. Realistically, that makes a compelling case for running as Local System.