When is a script closed (time of unregistering)?

Dear friends and experts!
To avoid one (or more) of the special effects reported in this forum Klaus Göbel proposes to unregister the script when it is closed. But: when is the script closed?

I did not get a formal education in interactive programming, hence I have no real clue about the process: what is calling what. My programming experience is in procedural languages starting with Fortran in the 1960ies.

Please point me to a document describing all this - the Scripting Guide does not tell. And of course JavaScript books don't either.
The only sample script using Notify is FM_Suppress_Alerts.jsx and this is absolutely simplistic.
My understanding is this:

• Starting the script registers it - 'purchases' a watch dog (IMHO not the same as registering an FDK client).
• After starting the script it establishes the menu and configures the watchdog called Notification.
• Within FM there is a nother watchdog barking at (the cat) Command when a menu item is selected.
• Command calls the appropriate routine and then sleeps again (return tells the watch dog: have done!)
• Notify is waked up on special events and calls appropriate routines (return tells the watch dog: have done!)
• After a user has performed a menu selection and the the requested functions have been performed: where are we in the script? At the end of Command? At the end of main (that's really unreasonable).

The main structure of my script is this:

// --- Windows ID must be set outside the dialogue function to be available for Notify functions
var wPalC  = new Window("palette","FM-calc : Handle #calc Markers",    undefined);
//... also wPalS and wPalDS  main ();

function main () {
  SetUpGlobals ();                                // all global variables and constants  SetupFMcalc ();                                 // get inital data -- debug to be set explicitly  SetupNotifications ();                          // notification trigger 'Change document' etc.  // --- During development switch between the two following statements:  SetUpMenus(); // uncomment for real work  //DebugMenu (); // comment for real work - debugging does not work with menus
}
#include funGlobals.jsx
//... more includes
function SetUpMenus () {   //...
}
function Command (cmd) {   //...
}
function SetupNotifications () {   //...
}
function RemoveMyNotification() {   //...
}
function Notify (note, object, sparam, iparam) {   //...
}
//--- now follow the functions directly called from Command
function OpenHelpFile ()
function DoFMcalcInSelection()
function DoFMcalcInDoc () 
function DoFMcalcInBook () 
function HandleCalcMarkers()
function HandleSeriesMarkers()
function HandleDocSettings()
//...And all the others which I want to have in this module

In the past I had the call of RemoveMyNotification in the call-back functions for the Cancel/Exit buttons in the panels. But now I guess that the best place would be at the end of the Command function: After anything has been done.
But: SetUpNotifications is within the main function and will not be executed anymore after the script has been started the first time.

I need a better insight, sigh!