I get this question all the time. The answer is it depends. The factors that you should use to find out how often to update the schedule are length of the project and the amount of upcoming critical activities that need to be closely monitored. The shorter the project duration the more updates will need to be done. The more activities that need close monitoring the more updates will need to be done. Ultimately the chose is yours and how closely you want the project monitored.
Mike Rowe
