Using Outlook 2011 in a Lion environment has recently started to slow with use.  Every 3-4 days of heavy Outlook use starts a degradation of speed, nearly a minute response time for scrolling, and other tasks within Outlook.  The only solution I have found is rebuilding the database.  Things immediately speed up but ten start to slow in few days.  Does anyone have any thoughts on why this is happing and how to stop it?