The regulation you are trying to follow comes from your regulatory agency, not BSA. It says you must report SARs to the board "promptly." Obviously, that time frame, like "beauty," lies in the eyes of the beholder.
I've seen banks criticized in their written report of examination for reporting to the board on a quarterly basis. If there is a standard expectation it would probably be that they should be reported in the next regularly scheduled board meeting in the month following the month when the SAR is filed.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.