设置自定义时间，显示NS​​UserNotification

Question

我通过以下方式创建NSUSerNotification：

NSUserNotification *notification = [[NSUserNotification alloc] init];
[notification setTitle:notificationTitle];
[notification setInformativeText:_informativeText];
[notification setSoundName:NSUserNotificationDefaultSoundName];

[[NSUserNotificationCenter defaultUserNotificationCenter] deliverNotification:notification];

我希望通知显示的时间超过几秒钟 如何自定义通知在屏幕上显示的持续时间？