[Sigia-l] Persona / Scenario development: diminishing returns after how many?

[Anthony Hempell]

Hi - wondering if anyone has heard of a "standard" or "baseline" number
of scenarios to develop, as a minimum? We have an audience which breaks
down into three major personas, and are considering doing just one or
two user scenarios for each.   Our project involves five to six major
task flows and about a zillion minor ones (it's huge).  

We're looking for some guidance on where we should draw the line...
anyone hear of a similar concept in scenario planning to Neilsen's
diminishing returns after 5-6 usability test participants?

Thanks
Anthony