I was just pondering this as I don't stick to a particular schedule with mine which might be a bad thing but they are usually wormed and de-flea'd about 3 times a year.
I just did them this morning which got me thinking really about what other people do.
They were last done in July when I spied a tapeworm in my spangles poo. My dogs roam around the farm and eat the occasional unsavory half rotten body.
We usually in the spring worm everything together - sheep / cows/ horses / dogs and cats.
The vet had never really advised me on a proper worming programme for my dogs, but then I have never really asked. Is there a protocol to follow?