For Pooled or AutoLogon sessions that have more than one step, such as a Drilldown screen, set this to true in order to call the Select or other subsequent steps more than once.
Usually, a Task with multiple calls, such as a Drilldown, will release the session after the final screen / step is completed. If you have a requirement to call that "last step" more than once, that is when KeepSessionOpen should be set true.
Note that when KeepSessionOpen is true, the appropriate method to release the session should be called when all uses for the session have completed.
Note: this property is not relevant to a 2008 Finite State web service generation project; its functionality has been replaced with the individual Task properties, OnTaskCompletion and OnTaskError.