When we lived in Sydney my dog went through a stage of getting fleas all the time. Turned out it was the possums. My dog, a working cocker spaniel, was on Frontline every 2 weeks but this didn't help. What we do now is switch him between Frontline and Advantix in 6 month intervals, applying every 2 weeks during the warmer months and every 4 weeks when it's colder. We also got a load of those Flea bombs from the supermarket and let them off in the house, garage, and in the garden. What I found helpful to kill the fleas on him straight away were those tablets that they can take orally but I can't remember the name of them. Oh, and we also got some Poss Off to get the possums out of the garden.