Here are the new guidelines for parasite control using a strategic 
deworming program rather than the traditional rotational program.  While
 I have been pleasantly surprised at how well this approach works, as 
you can see from reading this, its not as simple as deworming every two 
months with a variety of deworming products.
http://www.aaep.org/images/files/ParasiteControlGuidelinesFinal032413.pdf