I, too, sowed some N. asturiensis seed in June 2014. It was very fresh and given to me by Jennie Archibold. It germinated and emerged that year and flowered this. I think that fresh seed sown in June is part of the secret of success. I've taken to keeping my exchange seed in the fridge until May/June so that I can sow it when it might do the same in the wild.
I keep tulip and fritillaria seed similarly until September.
I haven't got the timing for Autumn flowering narcissus sorted yet but I think shortly after Christmas may be a good starting point.
Jack