I feel uncomfortable changing this behavior. There has been some changes to code to fix threading issues and trigger firings. Could you test with latest SVN trunk version?

I tried with the latest trunk and I am still receiving the same results.

I created a very simple job (that just logs to the common logger).

public void Execute(JobExecutionContext context) {

    try {

        if (Logger.IsInfoEnabled) {
            Logger.Info("Execute(JobExecutionContext) started. " + context.Trigger.ToString());
        }
        context.Result = "Success";
    } catch (Exception exc) {
        throw new JobExecutionException(exc);
    }
}

The quartz section of my configuration file is as follows.

<quartz>
    <add key="quartz.scheduler.instanceName" value="QuartzScheduler" />

    <add key="quartz.threadPool.type" value="Quartz.Simpl.SimpleThreadPool, Quartz" />
    <add key="quartz.threadPool.threadCount" value="10" />
    <add key="quartz.threadPool.threadPriority" value="2" />

    <add key="quartz.jobStore.misfireThreshold" value="60000" />
    <add key="quartz.jobStore.type" value="Quartz.Simpl.RAMJobStore, Quartz" />

    <add key="quartz.plugin.xml.type" value="Quartz.Plugin.Xml.JobInitializationPlugin, Quartz" />
    <add key="quartz.plugin.xml.fileNames" value="~/quartz_jobs.xml" />

    <add key="quartz.scheduler.exporter.type" value="Quartz.Simpl.RemotingSchedulerExporter, Quartz" />
    <add key="quartz.scheduler.exporter.port" value="555" />
    <add key="quartz.scheduler.exporter.bindName" value="QuartzScheduler.rem" />
    <add key="quartz.scheduler.exporter.channelType" value="tcp" />
  </quartz>

I then have a separate Windows application that connects to the scheduler application that has the following code.
private void TriggerJobButton_Click(object sender, EventArgs e) {
    this.mScheduler.TriggerJobWithVolatileTrigger("sampleJob", "sampleGroup"); }

If I schedule a Simple trigger to execute every 30,000 seconds, then I use the separate Windows application and fire the job manually, it seems to hold the manual job and run it the next time another trigger fires every time. I have not been able to get it to fire manually without waiting on the next scheduled job. As a matter of fact, if I attempt to trigger manually multiple times, it will trigger the job each time but ONLY when the next scheduled trigger fires. However, if I change the Simple trigger to be every 300,000 ms, it seems to work most of the time. However, I attempt to manually trigger a job within about 30 seconds of another scheduled trigger, the manual job waits to execute until the scheduled job executes.

My Quartz_Jobs.xml is below.

<?xml version="1.0" encoding="UTF-8"?>
<quartz xmlns="http://quartznet.sourceforge.net/JobSchedulingData"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  version="1.0"
overwrite-existing-jobs="true">
  <calendar type="Quartz.Impl.Calendar.AnnualCalendar, Quartz" replace="false">
    <name>cal1</name>
    <description>description0</description>
    <base-calendar type="Quartz.Impl.Calendar.WeeklyCalendar, Quartz" replace="false">
      <name>name1</name>
      <description>description1</description>
    </base-calendar>
  </calendar>

  <job-listener type="QuartzIntegration.JobListener, QuartzIntegration" name="iSolutions Job Listener"/>
  
  <job>
    <job-detail>
      <name>sampleJob</name>
      <group>sampleGroup</group>
      <description>Sample job for Quartz Server</description>
      <job-type>QuartzIntegration.LoggingJob, QuartzIntegration</job-type>
      <job-listener-ref>iSolutions Job Listener</job-listener-ref>
      <volatile>false</volatile>
      <durable>true</durable>
      <recover>false</recover>
    </job-detail>
    <trigger>
      <simple>
        <name>sampleSimpleTrigger</name>
        <group>sampleSimpleGroup</group>
        <description>Simple trigger to simply fire sample job</description>
        <misfire-instruction>SmartPolicy</misfire-instruction>
        <volatile>false</volatile>
        <job-name>sampleJob</job-name>
        <job-group>sampleGroup</job-group>
        <repeat-count>RepeatIndefinitely</repeat-count>
        <repeat-interval>30000</repeat-interval>
      </simple>
    </trigger>
    <trigger>
      <cron>
        <name>sampleCronTrigger</name>
        <group>sampleCronGroup</group>
        <description>Simple cron to simply fire sample job</description>
        <misfire-instruction>SmartPolicy</misfire-instruction>
        <job-name>sampleJob</job-name>
        <job-group>sampleGroup</job-group>
        <cron-expression>0/360 * * * * ?</cron-expression>
      </cron>
    </trigger>
  </job>
  
</quartz>

Below is a sample from the log file when it DOES not work. In both instances of the LoggingJob being calld by the Trigger 'MANUAL_TRIGGER.xxx' I triggered the job at least 20 seconds before the next scheduled job.

12:41:58.006 DEBUG Quartz.Simpl.SimpleJobFactory - Producing instance of Job 'sampleGroup.sampleJob', class=QuartzIntegration.LoggingJob
12:41:58.006 DEBUG Quartz.Simpl.SimpleJobFactory - Producing instance of Job 'sampleGroup.sampleJob', class=QuartzIntegration.LoggingJob
12:41:58.006 DEBUG Quartz.Core.JobRunShell - Calling Execute on job sampleGroup.sampleJob
12:41:58.006 INFO QuartzIntegration.LoggingJob - Execute(JobExecutionContext) started. Trigger 'sampleSimpleGroup.sampleSimpleTrigger': triggerClass: 'Quartz.SimpleTrigger isVolatile: False calendar: '' misfireInstruction: 0 nextFireTime: 08/31/2008 16:42:28
12:41:58.006 DEBUG Quartz.Core.JobRunShell - Trigger instruction : NoInstruction
12:41:58.006 DEBUG Quartz.Core.JobRunShell - Calling Execute on job sampleGroup.sampleJob
12:41:58.006 INFO QuartzIntegration.LoggingJob - Execute(JobExecutionContext) started. Trigger 'MANUAL_TRIGGER.MT_5934449982116256437': triggerClass: 'Quartz.SimpleTrigger isVolatile: True calendar: '' misfireInstruction: 0 nextFireTime:
12:41:58.006 DEBUG Quartz.Core.JobRunShell - Trigger instruction : DeleteTrigger
12:41:58.006 DEBUG Quartz.Simpl.RAMJobStore - Deleting trigger
12:41:58.006 DEBUG Quartz.Simpl.RAMJobStore - RemoveTrigger MT_5934449982116256437,MANUAL_TRIGGER
12:42:00.005 DEBUG Quartz.Simpl.SimpleJobFactory - Producing instance of Job 'sampleGroup.sampleJob', class=QuartzIntegration.LoggingJob
12:42:00.005 DEBUG Quartz.Core.JobRunShell - Calling Execute on job sampleGroup.sampleJob
12:42:00.005 INFO QuartzIntegration.LoggingJob - Execute(JobExecutionContext) started. Trigger 'sampleCronGroup.sampleCronTrigger': triggerClass: 'Quartz.CronTrigger isVolatile: False calendar: '' misfireInstruction: 0 nextFireTime: 08/31/2008 16:43:00
12:42:00.005 DEBUG Quartz.Core.JobRunShell - Trigger instruction : NoInstruction 12:42:28.010 DEBUG Quartz.Simpl.SimpleJobFactory - Producing instance of Job 'sampleGroup.sampleJob', class=QuartzIntegration.LoggingJob
12:42:28.010 DEBUG Quartz.Core.JobRunShell - Calling Execute on job sampleGroup.sampleJob 12:42:28.010 INFO QuartzIntegration.LoggingJob - Execute(JobExecutionContext) started. Trigger 'sampleSimpleGroup.sampleSimpleTrigger': triggerClass: 'Quartz.SimpleTrigger isVolatile: False calendar: '' misfireInstruction: 0 nextFireTime: 08/31/2008 16:42:58 12:42:28.010 DEBUG Quartz.Core.JobRunShell - Trigger instruction : NoInstruction
12:42:58.013 DEBUG Quartz.Simpl.SimpleJobFactory - Producing instance of Job 'sampleGroup.sampleJob', class=QuartzIntegration.LoggingJob
12:42:58.013 DEBUG Quartz.Core.JobRunShell - Calling Execute on job sampleGroup.sampleJob
12:42:58.013 DEBUG Quartz.Simpl.SimpleJobFactory - Producing instance of Job 'sampleGroup.sampleJob', class=QuartzIntegration.LoggingJob
12:42:58.013 INFO QuartzIntegration.LoggingJob - Execute(JobExecutionContext) started. Trigger 'sampleSimpleGroup.sampleSimpleTrigger': triggerClass: 'Quartz.SimpleTrigger isVolatile: False calendar: '' misfireInstruction: 0 nextFireTime: 08/31/2008 16:43:28
12:42:58.013 DEBUG Quartz.Core.JobRunShell - Trigger instruction : NoInstruction
12:42:58.013 DEBUG Quartz.Core.JobRunShell - Calling Execute on job sampleGroup.sampleJob
12:42:58.013 INFO QuartzIntegration.LoggingJob - Execute(JobExecutionContext) started. Trigger 'MANUAL_TRIGGER.MT_1281467642822479981': triggerClass: 'Quartz.SimpleTrigger isVolatile: True calendar: '' misfireInstruction: 0 nextFireTime:
12:42:58.013 DEBUG Quartz.Core.JobRunShell - Trigger instruction : DeleteTrigger
12:42:58.013 DEBUG Quartz.Simpl.RAMJobStore - Deleting trigger
12:42:58.013 DEBUG Quartz.Simpl.RAMJobStore - RemoveTrigger MT_1281467642822479981,MANUAL_TRIGGER

Yes, your solution seems to be perfectly valid and seems to fix the problem. Fix is available in trunk now. Thanks for your detailed problem report.