Ever since I updated to StuffIt 9, it took longer to start up than did the previous version. So I finally looked into the preferences. There I found and unchecked the Preferences -> Version Check tab -> Allow verson check box. I did this in the Expander as well as in DropStuff. Both now start up in about half the time.
Before this Stuffit used to look for updates on start up, which can take a while.
This should also work in older versions of StuffIt.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050127105408754