insertLabel() in Application object for persistent data storage

I thought about storing persistent Information in the Application object itself:

Not so interesting code snippet:

app.insertLabel("pxComplexName", "test");

// Later/Restart Safe

app.extractLabel("pxComplexName", "test");

I know how to get labels by extracting them from IDML. Does anyone know where the Application label is saved?

I thougt about using this as straightforward script usage counter in a trial version of a script. Any thougts about this?

Regards,

Gregor