https://twitter.com/idBrianHarris - 31st October
That's still only 2 weeks though; the Q2 3.12 patch took 2 weeks testing too - http://floodyberry.com/carmack/johnc_plan_1998.html#d19980222
It's also the case that BFG doesn't appear to have any crashers in it; no AMD hardware shenanigans, so perhaps that can be read as an indication that a patch doesn't need to be rushed out, so they can take a bit more time over it.
Optimistic, I know, but all the same: on balance a higher-quality patch later seems preferable to a rushed half-assed job. So long as it's not too much later.