I personally have never had a problem with thread necromancy, where old threads are revived. Some threads are simply so good it seems sensible to continue discussion in them, even years later, rather than start afresh. Sometimes, we just want to find out if anyone has considered something in detail before. In this post I'm just listing my index of threads I noted on demographics of the Order of Hermes. There is some great stuff in here I think, and hopefully this will make it a little easier to find it...
DEMOGRAPHICS OF THE ORDER
EDIT: The almost definitive article on this topic has not been created by Mark Shirley and can be found in Sub Rosa issue 14.
The Order of Hermes, Early Recruitment[/b]
Size and Shape of the Post-Schism Order
Magi of the Various Tribunals?
Too Many Magi
Hermetic Demographics: Where are all the Quaesitores?
Attrition rates for Magi
The High Level Limit of Ars Magica Fifth Edition
What if multiple apprentices were the norm in the Order?