Biannual's

biannual plants are hardy and will over winter as a juvenile plant just as you presume, maturing and flowering the following spring/summer

Lupin are a perennial but take a year to establish before flowering. It's also said that they are short lived, 3 maybe 4 years, although may gardeners will tell you theirs are older. It's really down to the plant tbh.

Biennials stay, slugs permitting, as small plants eg foxgloves over the winter months & then flower the next year. J.

Tina -I replied to your question last week on the same subject?

http://www.gardenersworld.com/forum/plants/biannuals/3980.html