The best way to permanently rid yourself of a flea infestation is to keep all the dogs and cats in your home on flea medication such as Frontline year-round, or at least during the active flea season in your climate area.
It can take a month or two to kill an entire flea infestation including flea eggs and all the adult fleas in an infestation, but once you reach that point you’re home free as long as you keep your pets on the medication.
That is because any new adult fleas that they may pick up in the yard or wherever they may travel will be killed before they are able to reproduce and lay more eggs, so the lifecycle of the flea population will be interrupted.
Without a viable host from which to obtain a blood meal, fleas will not be able to survive and you will in essence be able to permanently rid yourself of the problem. You may still notice an occasional flea or two on your pet, but it will be killed in a matter of hours.