Last spring I started my dogs up on Advantage flea control, thinking I would need to carry through with monthly application until November. Well, I ran out of it in June and decided to wait as long as I could before reapplying (not a big fan of chemicals). I am still waiting! I have combed off a few fleas in the 3 months, but no more than one at a time, with weeks passing before finding another one. What's amazing is that they go to the dog park several times a week and theoretically should be covered in fleas! I am guessing it is their good diet and regular exercise. I feed them Blackwood kibble for senior dogs (one of my dogs is young, but she gains weight fast on regular kibble), partially undercooked turkey or beef, and a teaspoon of molasses. I personally think that dogs who are infested with fleas are probably eating low quality kibble... if you've done your research, you know the kind of disgusting, cancer causing ingredients in the cheap stuff.