I have only started gardening 3-4 yrs. ago, and one of my first winter-sowed seeds were Lupines...and now I have them all over my garden (luckily in the spaces I want them to grow!). I love them. The reason they self sow is that when I started my garden site, the bed was well tilled and black dirt plus lots and lots of composted horse manure with a little wood bedding, ( we raise quarter horses, so I compost a lot of manure) about 10-12 inches deep was all tilled in before I planted anything, and I don't dead head them.
They are watered at least once a week along with my other plants (roses, peonies, daylilies, clemantis, etc.). I live right in the middle of Iowa, zone 5.
I thought I had sent in My two penny worth re this question but hey, It's now Friday and the weak ending!!!!!.
Lupins are one of the permissive plants along with Fox gloves ect, They are a short lived perennial and after the first 2 years the plants become weaker and the middle of the clump goes woody and less productive, they are really greedy plants therefore like a good dose of manure /good compost which offere nutrients and helps contain some moisture in the soil for longer which these plants also like.
When the plants are getting a bit poor in production, in early spring I like to Gently scrape away some soil around the growing stems this will expose several young tender rooted shoots, take a good sharp knife (a craft knife is good) and cut away a few of the tender side shoots WITH ROOTS ATTACHED, and depending on your temps / climate, insert the little cuttings into a new planting area OR into a pot and grow on in a sheltered area till large enough and the soil is warmer with added manure or compost.
These new plants will be a replica of the parent plant where as, seeds from lupins dont always come true as the parent plant as it depends or what other colour was pollinated by the bee's ect.
After about 4 years I normally discard the plants or take several cuttings IF I really like the colour, size ect of the parent plant and think I would like to keep that type growing another couple of years.
Hope this also helps you out a bit.
Best regards. WeeNel.