They're trying to figure out how often to worm, which is why I suggested having fecals done. OP is concerned about amount of time without eggs and probably doesn't want to every 3 months unless they have to.This is much cheaper than a vet and will last you at least 2 years:
http://www.jefferspet.com/safe-guard-dewormer-for-goats/camid/LIV/cp/I6-SK/
-Kathy