When using a flea pill you should always give your cats and/or dogs pills which are made for that type of animal, respectively. It is also important to take into account the weight of the pet as this should also relate to dosage. Most medication is meant for adult pets, so be sure that your animal is not too young. Pills are generally administered on a need-only basis and can sometimes be used daily depending on the pill. Of course you should always check the directions for whatever product you are using as every flea pill may be slightly different. There is a slight degree of debate circulating around how often you should administer a flea pill to your pet. While some people say that you should only medicate your dog or cat if they have fleas, others say it depends on the time of year, and still others claim that you should always give your pet flea medicine, all year around. Ultimately the choice will be up to you, the pet owner.
The presence of fleas is directly related to the temperature, so unless you are just going to treat your pet all year around no matter where you live, this is important to understand. Fleas are the happiest in warmer temperatures, especially when it is 65 degrees and above. They are moderately present in climates 40-64 degrees, and quite scarce when it is under 40.
If you live somewhere that it is warm all year around you might as well give you pet flea meds throughout the year. If you live in a warm climate you may also want to reconsider using a flea pill, as some of them will only last for a full day. Before you know it the fleas could be back. You may want to ask your vet if a spot on treatment or flea collar would be better, but many flea pills are safe to use on a daily basis. Make sure that the specific flea pill is safe to use with this much frequency.
If you live someplace that it moderately cold at least part of the year, you should only need to treat your pet during the warmer summer months. It is possible that fleas may travel indoors and thrive during the cold months, which is why some people suggest using continuous treatment throughout the year. You can also just keep an eye on your pet to see if fleas come back after you have given them a flea pill. As just mentioned, some flea pills are safe to use daily depending on the need.
If you live in an area that is really cold all year around then you probably won't need to use flea pills too frequently. It is also suggested to use flea protection right before the peak flea season, even in cold areas. Check out the kind of flea pill you are using as some will only kill fleas that have already infested your pet and don't work as well for preventative care. Ultimately how often you use a flea pill for your pet will hinge on the need and where you live.