My mom bred and showed dogs for years, and now that she is older and no longer breeding/showing, she still has 6 retired dogs. We used frontline for YEARS and always loved it, but in 2008 we got a very, very bad flea infestation. Im talking so bad they got into our house, and I ended up in the hospital in under 3 days because im allergic to flea bites and got red streaks going up my legs, NO FUN. A bit upset, because as you can imagine, frontline wasn't cheap for 6 dogs and 4 cats, all of which were house pets. Im not sure how the flea issue went from non existent to completely out of hand in a matter of friday - monday, but it did.
We bathed all animals in blue dawn dish soap and let it sit for 5 or 10 minutes wet, put advantage on two days later (when the vet was open to pick it up), flea bombed our house, washed ALL of our clothes, bedding, curtains, etc. Got a spray from our vet that was sprayed on our upholstered things such as mattresses, couches, chairs, etc. We went around the exterior of our fence about 8" out from the fence with moth balls all around the area where our dogs go out to potty. Knock on wood, we haven't had a flea issue since. I think the fleas got resistant to the frontline from us using it for so long, and thats why switching to advantage worked.
My mom does only use flea preventative after the first thaw, and until about late October now. They live on a few acres, keep their yard meticulously cut, and have no other dogs in the area.
I moved out in 2009 but still live about 1/4 mile from my parents. I have neighbors who dont take basic care of their pets, so im sure they arent spending money on flea preventative, so I do keep my dog on preventative year round (theres just a bigger risk here)