I live in the Northeast in a wooded are with lots of decaying wood.
Like the termites, carpenter ants are everywhere. I did have a living
tree next to the house that was infested with ants. The bottom of the
tree was eaten out and I didn't see any activity so I figured it was
inactive. When I took the tree down though, the solid part 6 ft up
and higher was infested. Got rid of those, treated the house and
figured I was ok. Then found a stump on the other side of the house
that was infested. Got rid of that last fall and thought I'd be ok
this year but started seeing ants again this summer and treated the
house again. Hopefully with those two sources gone I'll be ok next
year. I'll probably still have a preventative
treatment done in the spring.

If you can keep the wooden parts of your house dry and fungus-free,
the chances are good that the carpenter ants will leave it alone, anyway.
In addition to that, a wood-preservative/pesticide like boracare ought
to provide fairly persistant protection, and isn't any more toxic to humans
and pets than you'd expect. (By which I mean, don't use it on food-prep
surfaces, and if you burn something treated with it, stay out of the smoke,
and don't use the ashes in your garden..)

--Goedjn.