Sorry, but this is contrary to everything I've been taught and have encountered. Providing instrumentals and unmastered versions is not the same as providing stems.
Unless is was laid out in the contract beforehand (you DID have a contract with the band, yes?),charge for the stems. Especially if it consists of recalls. Sitting and bouncing out up to 16 individual stem tracks for each song on a record can be called anything but "real quick." Charge for your time working because no one is entitled to someone else working for free.
I just charge a reduced hourly rate for bouncing stems and prepping files.
It could easily take much longer than that, depending.