I use the once a month too ( K9 Advantix)... Before that came out, I felt my dogs had more chances of illness from shampoos, dips, sprays etc almost daily. Some were allergic to flea/tick/mosquitoe bites and would get horrible , painful hotspots .... not to mention tapeworm. Expensive ?? Yes. But so were vet calls. and meds . And yes, if your dog is around squirrels,rabbits,cats etc... you can expect fleas.