Yep, they are good for at least 3 years or more.
If you do propagate from it, my experience is that over-wintering new plants outside is far better than in a greenhouse or cold frame, despite what the experts have to say.
These were sown last year, and kept in big pots in my cold frame until March. I thought I was going to lose them at one stage:
This, on the other hand (I have 12 of these), sown at the same time, braved it outside huddled behind a bit of seaweed mulch to keep the worst wind off.....
