I was talking to a lady that said she gives her dog Heartgard every other month. She says that there is no reason to give it every month because it takes 2 months for the heart worms to develop to the next level and if you administer heartgard every other month you will still kill the larva and limit the amount of "poison" the dog is exposed to. Everything I have read says to give it every month but what she said kinda makes sense. Anyone know the deal? Is this lady playing with fire or are Vets and drug companies just trying to sell us more stuff?