I didn't know you were supposed to routinely give a de-worming pill every three months? I just bring in a stool sample when we visit the vet for routine checkups on the glands or whatever, they check for parasites at that time. We have always been negative for internal parasites so far.
We use Advantage for fleas, spot treatment once a month. Will be changing to Frontline Plus to include tick control once we start traveling with her into areas that are known to harbor ticks.