I'm back now a week later - family was kind enough to spray again at day 3, and I arrived home to a jungle of tomato plants, with no hornworms, yay!!
b54red: thank you for the powdered B.T. link!! I have liquid concentrate for this year, which has a shelf life of only a year. The powder form lasts 3 years according to the literature, and is only a few bucks more expensive than the liquid concentrate, so I will get some next year.