TopSpot is what I've been referring to as "regular" frontline.
Does TopSpot prevent you from getting an "infestation"? Fleas wander by all the time. I'd rather not cross the line between here-a-flea-there-a-flea and OMG-fumigate-the-place. So I use Plus because I figured it was the way to prevent the bigger problem. I'm still not sure if alternating them is effective.
swamper:based on some toxicology studies my grad student friends are doing, I was going to switch to Advantix
What are the studies? I know several people who switched to Advantage because Frontline stopped working for them, but I had heard there were issues with Advantix being a little too toxic.