Portlets Initialize method

I’m having trouble understanding the event model of the portlets that are created using designer when implementing a human based task. I’m using the WebMethods 7.1 Suite.
I used to believe that the Initialize method that is already created when you create a portlet is fired when there is a “page load” of a task instance.
For example, let say that we have a process that implements a human based task called approve order. In the Initialize method of the approve order portlet we invoke a flow service of the Integration Service via a web service connector. Once you run the application and have several process instances there will be a moment when in the inbox you will have more than one task instances of the task type Order Approval.
Now this is the rare part:
When you enter to the first instance of the task type the initialized methods will be fired, and the flow service called, but never again for the other instances of the same type until you log off and log on to MWS.
Is that a bug or the expected behavior? Is there a method that is trigger for each task instance and not for each task type?
Also, if you enter to another instance it seems that some of the fields of the form keep the values of other task instances.
Do I need to clean/reset all the control each time I enter to a task instance?