Wow, sounds like our dilemma with Fire Ants we had least year. We moved into our new house May 2010 and after a few months we'd see a fire ant here and there inside, but I didn't think anything of it until we started seeing HUNDREDS of them. They entered through the sand trap under one of our bath tubs and from there entered the walls, worked up the vent pipe into the attic, then went basically all over the house dipping into almost every room following the plumbing and wiring. It was TERRIBLE, but we've been working with a pest control company who is keeping the yard baited plus we've sprayed under the tub several times with Termidor (which is the BEST for ants of all kinds) and they're under control for now (knock on wood). It's been about two months since I saw one, but I'm constantly watching which I'll probably do at least until next winter.

The key as many have said is to keep the yard baited and also put down bait or whatever you can inside as needed. We only had them in the kitchen once when they came down through a column from the attic, but cutting off their source into the house (under bath tub) has seemed to be the biggest thing.. I'm also in the process of talking to the builder to have that sand trap covered in concrete, and if I ever do need to get in there, well I'll cross that road when I need to. Living Fire-ant Free is more important

But yes, as others have said, don't celebrate until you've gone at least a few weeks to a month or more without seeing any ants. Torro is good, but the best thing youc an do is get the outside baited. And check out Termidor -- that stuff is golden.