I do all mine once a year with Strongid, usually, sometimes Panacur. I only do it that often because I feed alot of wild game and fish--and my dogs are big hunters, they like to eat squirrels and mice so the odds of them getting worms are little higher. With so many of them I could never figure out who's got what from a fecal exam so I just do them all at the same time.

This year I did them all with Droncit, but that darn near broke the bank. It was over 500 bucks. Strongid and Panacur are much cheaper and my dogs think Strongid is a caramel flavored treats! Silly mutts!

When I had fewer dogs, I had fecal tests done if I suspected worms and then medicated with whatever the vet recommended.