Officially they "process checks" the last day of the month following the shop. Oddly enough it used to take them 10-12 days to "process checks" and they would be mailed around the 12th. The last 6 months or so it has taken them 15 or so days to "process checks."
FWIW. I could process a check in about 3 minutes.
There are reasons that a body stays in motion
At the moment only demons come to mind