silkworm life expectancy?

I'm thinking of ordering silkworms off the internet, because at the pet store theyre $1 each! So I just wondering if anyone knows, how long do silkworms last? I was thinking about buying 100 at a time, and that would probably last me several months, IF they lived that long. So does anyone know the life expectancy of a large silkworm (about 2'' long)?

I guess not.

At 2" the silkworms either become moths or die before they make it several months.
When I kept silkworms I always just bought several thousand eggs, hatched them out and fed them out that way.