Finishing in a timely manner is also crucial. If everyone agreed that the meeting would last an hour, the meeting should not run any longer than that. Keeping the agenda realistic is important, of course. Finally, if only 20 minutes are required to accomplish the meeting objectives, the meeting should end after only 20 minutes. It would be a waste of everyone's time to let it go on any longer than that.
The time at which the meeting is scheduled is also important. Scheduling regular meetings for inconvenient times (e.g. after the end of the official work day) can have a very negative impact on morale. Emergencies are a reality for most organizations and may necessitate meetings at odd times, but routine meetings should be scheduled at a time that is reasonably convenient for the participants.