First off, if you aren't currently treating for termites with a soil treatment and/or bait system, start now. It will save you thousands in the long run, and you won't have constant fears of termites like I now do.
Anyway, about two years ago, I was sitting with my partner, watching TV in our basement. My partner got up to do something, and noticed that at the bottom of our basement bathroom door frame, there was what looked like dirt. A closer inspection revealed that it wasn't dirt, much worse. This was termite frass, further confirmed by the termites visible in the frass.
I quickly did research and bought termidor foam (It should be noted that Termidor foam only lasts 6ish weeks, and is meant to be applied directly to areas with active termite activity), dominon, and boracare off of domyown.com.
I applied the foam, dug trenches around the house to treat soil with dominion, and waited about three months before fully demoing the bathroom. Inside of the wall closest to where my partner noticed the frass, there was a huge mud tube that seemed to have multiple chambers inside of it. This tube chamber was probably about 4 inches by 5 inches. This tube stopped about 4 and a half feet up the wall, and did not appear to go into the upstairs area. The sheetrock's paper between the paint and gypsum had been eaten away into tunnels as well.
(Slight side note, at this point, I was confused as to what type of termite I was dealing with. I knew that usually, subterranean termites don't create frass as they use that to build their tubes. I now know that they can actually create frass piles when they accidentally break through the wood. This can cause the frass to spill out. If this hadn't happened, we probably wouldn't have figured out that we had termites until it was too late.)
I could not identify any damage to the studs, and they seemed very sturdy. Boracare was applied. We sheetrocked and fixed up the bathroom over the next little while. I'm unsure about their entry point. During the repairs, I found a relatively large crack in the slab, right underneath the wall for the bathroom. I'm guessing this is how they got in, but can't be sure. I pumped it full of concrete silicone, used at least 3 tubes worth.
Maybe about a month later, I found more evidence of termite damage, this time behind my furnace which is in the center of my basement, maybe about 10 feet away from where I found the original tube. There was frass along parts of the very old, 1940's baseboard. I have no idea how they got there, and still am not sure how long they had been there. Nonetheless, once I noticed the frass, I immediately got my extra can of termidor foam and filled the void between the wall and the baseboard. Since doing that, there has been no new visible frass, and we haven't found any swarmers. I'm honestly too scared to cut a hole into the wall to assess the damage, and might ultimately have an inspector come out and check it for us.
I'm increasingly paranoid about them. I constantly think that every squeak in the floorboards upstairs is caused by termites. Any dip in the flooring, no matter how slight, sends me into another bout of paranoid reading about how termites are eating away at my home. Maybe about an hour ago, after another one of these spirals, I bought a pack of 10 bait & monitor systems which I plan on putting around the soil outside.
I guess, to sum up, you should be treating your soil for termites, even if you have never seen signs of an infestation. If you live in an area with a lot of subterranean termites, buy baiting systems so you can monitor if your property is having any termite activity, on top of the soil treatment. If you're not comfortable doing it yourself, hire a pro. It's worth it to treat for termites as if an attack is inevitable.
I hope that one day, I feel confident that I got them. Unfortunately, without tearing out all of my walls and floors, I can never be sure at this point. It's a horrible feeling, and don't want anyone else to experience it. I've lost countless hours of sleep.
The only reason my partner and I got married was to make insurance and taxes easier. Otherwise, we wouldn't have done it. Only three people were at our wedding which was in our living room.