Species question

Dear All who answered privately and asked me to forward the answer when known (to the question shown below):
Very interesting facts and estimations were sent to me by Mr. Michael Berrigan. However he told me today that he will probably put this into an article once the complete picture is known, since he has a little research to do.
So, while thanking him for now, we will have to wait a while for his final conclusions.
Best regards
Henry

—– Original Message —–

Dear Daffnet Users,

We all know that most daffodil species and all man-made varieties multiply also through agamic production of bulblets. In this sence one could say that – in adequate conditions – the plant, in its clones, is practically eternal.
What does not seem to be of common knowledge is the life span of a single daffodil bulb. It will be internally renewed from year to year and it will grow in size but what is known about the life expectancy of that single plant? Are there plant, or better daffodil, physiologists who would like to tell what is known in this respect, possibly referred to daffodil types (divisions)?
Thanks to everybody and best regards.
  Henry (Rome)