Well, I conflated a rate and current authorizations from here: Trial Rate Limit Adjustment Request Form
Issuing certs across time works if you can be predictive, but if you need to do it on demand, spread out across each week, you cannot account for new domains versus renewals for pipelining. So if the expectation is to issue a dozen or so requests/week (not 12 every week on a specific day, but more on the order of 2 or so per weekday), is that when it become appropriate to request an exception?