How many did you buy? When I started buying them from a local shop here (last year) they actually came in those upside-down containers with that gooey food they eat, so they lasted a week if I wanted. That shop has since closed though and now where I get them, I just get a baggy.
Hornworms (the big ones) in terms of nutrition are equal to 30-48 crickets depending on size. So I'm not really sure where you heard they have poor nutrition levels. They are up there with Dubias and Silkworms (the best). So if you have an adult, which I think you do, one a day sounds about right (for some of the biggest ones)?
I usually kept them in my basement to stay cool. I gave them a couple pieces of endive/escarole and 2 or 3 would usually last 3-4 days max before their color started to go down-hill. I usually only buy 4 at a time (2 green plumed basilisk) and they eat these mainly with their crickets/dubias. I refrigerated once and they died, so I won't do that again.