Committees should meet as often as necessary to accomplish their work.
Form follows function. Committees (and task forces) should only feel compelled to meet when there is substantive work to be done. For example, a Facility Committee racing to close a deal on a new building might need to meet every week for six weeks straight, whereas the Academic Committee might need a standing meeting once a month to review the school performance data. The frequency of the committee meetings should correlate with the board meeting frequency and the committee's responsibilities. For instance, if the board is meeting 10-12 times a year, it is common for the finance committee to meet monthly.
Remember, substantive committee work in between board meetings is one of the keys to an effective board. See our article on Committee Work Between Meetings.
BoardOnTrack Recommends...
To the extent possible, map out all your committee meetings for the year, and get them on your committee members' calendars. Volunteers are busy people, and it is much more likely they will come to meetings if they know about them far in advance.
If you are unclear about how many meetings you will need, it is better to pencil them all in. It is easier to cancel meetings than it is to ask busy folks to schedule them at the last minute.
Updated