I was doing some investigation into the inner workings and some of the more useful properties on the iterator bindings in the page definition xml files to to satisfy my curiosity.
So here are some findings I have to go into much more details than this but this should help someone.
I had a basic page with one iterator (driving a select one choice) two buttons one with an action one with an action listener and a child iterator driving a table.
I use any number of Refresh parameters on my page (always, deferred, ifNeeded) etc and the method bound was only called once on pressing any button or autoSubmit - all good.
I the set the CacheResults parameter to false this lead to my method being called a number of times and some weird but expected behaviour still good.
Now I changed to a methodIterator from a accessorIterator with one parameter and returned null from the data control. The method was now called a number of times with a null parameter not good. I changed the return null to return an empty list and everything started working as expected.
Need to still check immediate, partialSubmit, changeEventPolicy and a few other attributes but this answered some of my questions.