Thanks for the link. Yes, that's one of the articles I read, and which helped me to realise that I have a major and on-going problem which needs patience, patience and yet more patience, given these facts:
"Seed longevity in dry storage is 12 years and in soil is 35 years. Charlock seeds buried in uncultivated soil will remain viable for 60 years"
Also:
"The optimum germination temperature is 21°C and there is little germination below 11°C or above 30°C."
We've had single figure temperatures for weeks now, and that hasn't stopped the stuff germinating!
But that's taking the subject from the general to the specific. To give other examples, nettles can live for about five years, and chickweed, three.