After spending several hundred dollars every year on sprays and such (bayer, dominion and countless others), I always had fleas of some sort. I kinda kept them in control, somewhat... I went to comfortis 2 years ago. In my opinion you cant go wrong. I spend about $250 bucks a year, I have 14 dogs (counting puppies) and I promise you that you can't find a flea on any of my dogs. That stuff turns every dog into a flea killing machine!!!
I have done the same. I use Mr. Mike's method of crushing the pills, mixing it good, and using half/ dog. Works just as good, but half the cost.