Signs fire ants are under control or gone under house foundation.

I've posted a few times about our fire ant problem in our house in Central Texas where in September 2010 we had a full infestation of fire ants within our newly constructed house. But it seems, hopefully, that they're finally under control, but I wanted to post some notes about what we've seen in hopes that others can give more info.
Wed, Dec 22nd our bug guy came out and sprayed inside the walls of our house with some chemicals that he said would kill them within 30 minutes to an hour, then he heavily baited outside the house. We didn't see any ants until around Monday, Dec 27th when we saw about 10 ants come out in the bathroom then nothing. Since then I saw two ants last month, both appeared to be fully mature (larger than most) and that's been it... last one was almost a month ago.
Granted we're in winter, but other then last week our temps have been in the 50's to 70's even hitting 80 once or twice. We even had a couple of weeks with little to no rain, which has often been a driving force for the ants to move inside. But in the last month nothing.
My hypothesis is that the ants took in the bait and the influx we had a week or so later were the workers just going where ever they could. Also the two larger ants we saw in January I hope were just wondering workers that just made it inside with the colony being gone.
Does this sound reasonable? If the colony was still alive I'd think they would still be showing themselves, especially if they were spending the winter under the house foundation.
Also note to those who haven't read my former posts, the ants have been entering our house through the pipes that come through the foundation. We had termidor and some other chemicals sprayed in the wall voids which helped, but nothing solved it.
I really hope as spring comes we don't start seeing a renewed influx of fire ants as it gets warmer, but given fire ants don't hibernate hopefully what we're seeing is a good sign.
Thanks for any insight --
Sam Alex
last weekend we had sub-freezing temps but the last two weekends we've had temps in the 60's, 70's, and even hit around 80 once.

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