"sue and dave" writes:

I'd encourage you to scale back your expectations for an 8'x16' lavender bed
and look to a container situation for lavender, maybe 6-8 plants nursery
grown to transplant stage.

I'm in the very same USDA Zone 5B, adjacent to the Androscoggin River in
Western Maine

If its lavender you want, for scent, for packaging, or for sale in any way,
you ( and I) just don't live in the right part of this world to have it as
a perennial.

I'm surprised to read this, as I'm in zone 5 (a or b I'm not really
sure - sort of on the cusp, so far as I can tell) and the lavender
plant my great uncle from Olean, NY (zone 4b or 5a by the map I see)
gave me from my garden in the early 1970s throve for years. When I did
notice it dying back after 15-20 years, I grew a new plant by rooting
a cutting, and that plant is now doing pretty well itself. Maybe I've
just been lucky?

To the original poster: how about buying a few plants and growing more
from cuttings, if seeds turn out to be a pain?