We don't employ a strict time limit simply because different topics require differing amounts of time to present and discuss. For example, the committee presentation regarding our school carnival will take up most of the meeting time during the PTO meeting a month prior to the carnival. Conversely, a teacher request for funds to stock her classroom library can be handled in just a few minutes.
If there is any given board member or committee that is taking up an extra-ordinary amount of meeting time on a regular basis, it's up to the board members to keep to the agenda and move things along. Sometimes, it's just a matter of a gentle reminder to "finish up" when the presenter has presented all the info but then starts to re-cycle the same details over and over using different words each time. In other situations, the board needs to work with the committee or person scheduled to present prior to the meeting to set boundaries for their presentation.
If the issue presented is not on the agenda, the members should take control of the situation so that the agenda can be followed. In parliamentary parlance, a "Call for the Orders of the Day" is a privileged motion by which a member can require the assembly to conform (i.e. follow) the agenda, program, or order of business in the prescribed order.
