 Millen announced his intention to retire from first team football in June 2008.During his time with St Mirren, he won the Scottish Challenge Cup and the Scottish First Division in the 2005–06 season.Millen's last league appearance was against Hearts on 15 March 2008, which meant that he set the SPL record for oldest player at 42 years and 279 days, almost a whole year more than the previous record.