Using Microsoft.EnterpriseManagement Namespaces, Why is the PartialManagementObject.StopMaintenanceMode function ignoring the endTime parameter

I'm using PartialMonitoringObject.StopMaintenanceMode to set maintenance modes on Microsoft System Center Operations Manager 2007 R2, check here. No matter what I do, it seems to be ignoring the end time and ending my maintenance window immediately no matter what I specify. The code looks like this:

foreach (string SCOMServer in SCOMServers)
{
    ReadOnlyCollection<PartialMonitoringObject> windowsComputerObjects;          
    ManagementGroup managementGroup;
    MonitoringClass windowsComputerClass;               
    managementGroup = new ManagementGroup(SCOMServer);           
    windowsComputerClass = managementGroup.GetMonitoringClass(SystemMonitoringClass.WindowsComputer);
    windowsComputerObjects = managementGroup.GetPartialMonitoringObjects(new MonitoringObjectGenericCriteria("Name='" + ServerFQDN + "'"), windowsComputerClass);


    foreach (PartialMonitoringObject windowsComputerObject in windowsComputerObjects)
    {
        if (windowsComputerObject.InMaintenanceMode)
        {
            windowsComputerObject.StopMaintenanceMode(DateTime.UtcNow.AddMinutes(DelayInMinutes),Microsoft.EnterpriseManagement.Common.TraversalDepth.Recursive);
            //  windowsComputerObject.ScheduleMaintenanceMode(DateTime.UtcNow,DateTime.UtcNow.AddMinutes(DelayInMinutes)
            RetVal = true;
        }
    }

    `

Solution

Not sure why the StopMaintenanceMode command doesn't work as documented, but changed the code to use UpdateMaintenanceMode instead, and it now does what I need it to do.

foreach (PartialMonitoringObject windowsComputerObject in windowsComputerObjects)
                {
                    if (windowsComputerObject.InMaintenanceMode)
                    {
                        if (DelayInMinutes == 0)
                        {
                            windowsComputerObject.StopMaintenanceMode(DateTime.UtcNow, Microsoft.EnterpriseManagement.Common.TraversalDepth.Recursive);
                        }
                        else
                        {
                            windowsComputerObject.UpdateMaintenanceMode(DateTime.UtcNow.AddMinutes(DelayInMinutes), MaintenanceModeReason.PlannedOther, null, Microsoft.EnterpriseManagement.Common.TraversalDepth.Recursive);
                        }

                        RetVal = true;
                    }
                }