hey, i know this was posted a while back, but im having a similar dilemma. I was wondering if there was a certain time in which to use the wormer...does it have to be every 2 weeks till they pass ;( - which could be hopeflly another 15 yrs away, or just for a while like a few months course? i was thinking theyd develop resistance to the med if used over years. Did you end up buying the vet med and how did that go? thx for any help.