The committee that is in charge of making sure your organization has enough well qualified candidates to sit on your board will have work to do all year long, not just before the annual general meeting (AGM).
At the AGM a slate of directors will be presented to the membership or shareholder for election to the board. This is what we would call planned succession. However, there are circumstances when board members leave the board during the year. Perhaps due to conflict with the other board members, due to illness or because they are asked to leave. This is emergency succession.