Yes, as often as you wish. The change is effective from the date you make the change and beyond. You cannot change causes retroactively.
To change the cause you're supporting, click on Settings.
Then, click on
My Favorite Cause
Change Settings
Article ID: 108, Created: 3/8/2010 at 3:00 PM, Modified: 5/15/2015 at 3:04 PM