When to update NSFindPboard

What are the appropriate times to set NSFindPboard?

I can find really very little information about this in the =
documentation, basically nothing, and the only sample I could find is =
very limited in this respect, too little to give any useful information.

Also, looking at various Apple applications I can actually find several =
different behaviors.

So here is my setting. A window containing searchable information, which =
can have a scope bar containing a search field. The scope bar can be =
added and removed, and searching can be done through =
performFindPanelAction: or buttons (more precisely an segmented =
control). So similar to Xcode 3's edit windows.

So there are a few things that can happen:
1. find (replace) actions, including search field action (Enter)
2. set find string (NSFindPanelActionSetFindString)
3. add scope bar
4. remove scope bar
5. window becomes key
6. window resigns key

Would the correct behavior be to update the NSFindPboard in 1, 2, 4, 5, =
6? Or perhaps only when the find string is not empty? Or only at a =
subset of these events? Or did I forget about events that should trigger =
updating NSFindPboard?

thanks,
Christiaan