Auxiliary Constitutions and Recruitment: some thoughts

It's become quite clear that spending too much time with one person is bound to bring some disquietude.  And, I've been spending too much time with Procopius.  So, where possible, I've taken a little break to continue work on finishing up a project on the Roman military in the Moesias.

Today I've been thinking about auxiliary constitutions (the official citizenship document in Rome) and diplomas (the copies, the ones found all across the empire), and the related matter of recruitment.  Just read a paper by Paul Holder on copies of constitutions.  He calculated that if every province with auxiliary units had men eligible for discharge every year there could have been some 4,000 men "recorded on the original bronze constitutions set up at Rome".  That's a staggering number - and as I said just an estimate.  The figures that supported his claim include:  c. 50% of serving men lasted 25 years and so were eligible for discharge; 10 men each year from a quingenary unit (about 500-man unit); 18 men from a milliary unit (about 800-1000-men); 370 units in existence during the reign of Hadrian.  A number of questions popped into my mind upon reading this (and some of this other observations).

First, if those numbers hold up, and they don't seem unreasonable to me at first glance, how many bronze constitutions might have been produced and stored in Rome each year?  Would there necessarily have been just the one constitution issued per province per year?  Would the government want a record of each soldier?  Depending on how the numbers add up, we could be dealing with a staggering number of documents kept by Rome.  Would there be some sort of file for each soldier that tracked his record throughout his career?  Would this be in Rome, or would it just be an outline, so to speak there, with the details in his respective province?  Or, would it all be kept in his province?  And yet, many soldiers moved around (or those with some initiative might), and so would a file move with him?  Perhaps these would have been on less permanent materials, and only the really important stuff, like discharge certificates, would be recorded on permanent materials.  Anyway, it might be that this is unanswerable, but I thought I'd ask anyway.

The other issue alluded to above was recruitment.  Should we expect regular recruitment, that is a consistent number of men each and every year?  Or was it always, or partly, a hodgepodge approach?  Things are happening in province X, how many men are in province X, and so let's then raise Y men to compensate.  Most likely it always did vary - we know additional units (both auxiliary and legionary) were raised at different times.  Some units were lost, some were depleted, and some additional ones were needed for major campaigns, like Trajan's war of conquest.  I guess that means we should expect some 25 years or so after the start of a major campaign that there should be an explosion, of sort, of men available for discharge.  And yet, these new units often weren't disbanded once a war ended.  A unit might move on, but they didn't get dissolved just because a war was over.  Perhaps then it's a series of steady periods of recruitment followed by giant spikes at war time (major war).

I think I might be rambling now...so...best stop.  Besides, I have some diplomas to read/compare, and some more reading to do.  Thinking too about the merits of updating Watson's The Roman Soldier.