Program treats fleas by effectively sterilising any female fleas which bite your pets. Program does not kill any fleas as such, it allows them to live their life and die. It is actually very effective at treating fleas and you will never have a flea problem, as long as :-
You must treat all the time, not wait until a few fleas are around, then start treatment.
You must treat all animals in the household.
It seems that even dogs or cats with a flea allergy can tolerate a very occasional flea bite, but they react badly if they receive bites regularly and frequently. As long as the flea population is kept to an extremely low level, your pets will not react and you will never see any fleas. It does not sound very convincing, but in fact it really does work. However, if you are seeing fleas, that always means that there are loads about, and Program will be very slow to get rid of them. It will stop them breeding, but you have to wait for all of the fleas to die. Any eggs laid before you started Program treatment will gradually hatch out, over a period of maybe a few months, then those fleas will bite your pets.
It is always recommended to use something for adult fleas and ideally a household insecticide spray initially as well as Program if you are actually seeing fleas. If you continue to use Program, it will act as a preventative for future problems, but it is very slow at eradicating an existing flea problem.
I would suggest you buy some frontline Spot-on and some Indorex flea spray for the house too. Once they have been used, then afterwards just using Program will be fine.