I think you do what works for you. Even if you've gotten a small dose of Ivomec periodically, has it done you any harm?

Most vets I know who know anything about goats recommend drenching at a rate 1.5 times than the rate for sheep, and then drenching again 4 days later, because the digestive system of the goat quite a bit faster, and things stay in the rumen for less time, so aren't absorbed as well.
How often do you find you need to drench? We only do it on as as-needed basis with our goats, except for the annual post-kidding drench that the does get. And we are majorly overstocked, by NZ standards.
Even then, I will offer the goats anti-parasitic herbs before I drench if they are looking peaky (anemic or scouring). If that doesn't work in a day or so, then they get the chem drench (and we use a 3-way drench). We have to work with drench resistance in the majority of the parasite populations in NZ, but I also think it's becoming a worldwide problem.
What is your stocking rate, and how often do you drench? have you ever done a fecal exam to see what parasites you're dealing with, to make sure the ivermectin gets them all? There are 3 drench families, each of which targets different things, some overlapping, but they each won't get all, if I'm making any sense?
Cheers
Andrea
NZ