your lupins should be OK for next year. They don't live for too long though. You need to cut off the flower stems now, and you may get more flowers after, but you need to do it so the plants can put their energy into growing, rather than producing seed. If you want to save seed, you'd have to let a flower stem ripen and then collect the seed pods when they're dry. They don't come true to seed though, and would not be as nice (probably)
our lupins always get blitzed by aphids anyway
