Dottie, I never thought about Terro becoming ineffective as it ages, but
I went through my old bottle the 2nd day and bought a new one and used
it the next 3 days. I still had ants for the next 7 - 10 days so I
don't think age was an issue, but thanks for the tip.
Terro usually works pretty quick and now 2 or 3 weeks later the ants are
gone, so that's why I thought they might have completely killed off the
termite colony.

Normin & Phisherman, The siding is 4' wide sheets so the seams run
vertically. The mud lines along the seams start at the floor and go
about half way up. I suppose I'll peel the corner of a sheet away and
see what it looks like inside. Hope they're all dead or gone!