One way to do this would be to create a list of tasks with no due date and duplicate the entire list each time you want to reuse it. Unfortunately, the "Duplicate Task" functionality is not currently available in the iPhone app; this part of the process would need to be done using the web app.

To duplicate your entire list in the web app, select the list, then select all the items (the 'a' key is a shortcut for this), then choose "Duplicate Task" from the More Actions dropdown box. You can then move the new tasks and set the due appropriately.

Hope that helps!